First off, take a look at the Monitor Types comparison section of this site to get an overview of the basic types of monitors, and what some of the pros and cons of each of those choices are.
One of the big things that I wanted to change between AP2 and AP3 was the size of the monitor: I wanted something bigger than the 19" PC monitor that I used on the first two cabinets. It just plain wasn't big enough...especially on the vertically-oriented games.
I disqualified using a PC monitor on this cabinet right off the bat for a couple of reasons: First off, a PC monitor in the size that I wanted (approx. 25") would have been horrendously expensive, and secondly, while a PC monitor does look great for Windows and other PC applications, I felt it looked too "cartoonish" for an arcade display.
So my decision came down to an arcade monitor or a TV. I think that the consensus with most people is that an arcade monitor does look better than a TV, but in my opinion this argument rockets toward a quasi-"law of diminishing returns" situation rather quickly. What I mean by that is this: Okay, let's say that you do come to the conclusion that an arcade monitor does look better than a TV. You need to ask yourself "How much better does it look?" and "Is it worth the price and the bother?"
Let's take a non-arcade example: Let's say that you're in the market for a performance car. Model A can go 0-60 in 5.6 seconds, while Model B can go 0-60 in 5.4 seconds. Model B is clearly faster than Model A, but do you really care about the 0.2 second difference? And if you do care about that 0.2 second difference, how much do you care? How important is that 0.2 second difference to you? What are you willing to pay for it? And here's something else to consider: What if Model A has a more comfortable ride than Model B? Are you also willing to overlook comfort of the ride in favor of performance?
Hey, maybe these things matter to you and maybe they don't. There's no right or wrong answer here, it's just something that you will have to decide for yourself. You need to ask yourself "How big is the difference between the two, and how important is that difference to me?" For me, the look of an arcade monitor over a TV just plain wasn't worth the price and/or the hassle, simple as that. I experimented beforehand with a PC hooked up to a TV via s-video and I was very pleased with the results, so I went with a TV for my monitor. After shopping around, I decided on the JVC AV-27320 27" TV. The screen is nice, it displays from my PC beautifully, and as an added bonus, it has s-video input and component (Y, Pb, Pr compatible) input on it too! And yes, I do have a cable line running to it so I can watch TV on it if I want to.
The JVC turned out to be perfect in its size too, because the TV is 25-3/4" wide, which left me with 1/8" of play on either side of it (the interior width of the cabinet is 26"). I know that's kind of dancing on the edge of disaster playing it so close with the measurements, but the nice thing about it being so close is that I didn't really have to futz around with aligning or securing the TV at all. It can't go anywhere!
(Interesting side-note to all of this: In the Monitor Types comparison page on this site, I have a link to a page on OSCAR Controls' website that has a bunch of monitor close-up comparisons showing screenshots through a variety of monitors. Before he put that page up, Kelsey from OSCAR Controls held a contest on the BYOAC message boards where he asked if people could identify which screenshot belonged to which monitor, and wouldn't ya know it - most people couldn't.)
Even though I used 1x1s to attach all of the cabinet together, I didn't think that a shelf connected with 1x1s that were glued and screwed to the side would be strong enough to support the weight of the TV...that sucker is pretty damn heavy. My first approach was to use 2x4s that were glued and screwed to the shelf, and were then connected to the sides of the cabinet by 1/2" carriage bolts going through the sides of the cabinet and the 2x4s. But even that didn't quell my paranoia about the weight of the TV, so I also made a couple of additional braces out of 2x4, and I screwed and glued those directly underneath the main 2x4s that were attached to the monitor shelf.
I'm sure that this was way overboard for what I needed, but you have to remember that I'm not exactly a professional carpenter here, so I'd much rather adhere to the "better safe than sorry" mentality. Besides, the last thing that I wanted was some nagging doubt in the back of my mind about the strength of the monitor shelf. Now I know that it's not going anywhere no matter what.
TV shelf mounted with 2x4s and carriage bolts through the sides (back view).
Super-duper overkill braces underneath the TV shelf (back view).
On the recommendation of some folks at the BYOAC FAQ message board, I decided to try smoked (or tinted) plexiglass in front of the monitor. Wow, the results are amazing! The smoked plexiglass actually works as a "filter" of sorts, keeping the dark colors dark while allowing the bright colors to shine. It's one of those things that I wouldn't have thought made that big of a difference until I saw it for myself. If you want to see for yourself, OSCAR Controls has some really good side-by-side comparison pictures.
Another really nice thing about using smoked plexi is that I didn't have to use any kind of monitor bezel at all! The plexi is dark enough that you can't see the edges of the TV; in fact, all you can see is whatever the screen is showing you. The remote control for the TV works through the smoked plexi just fine too, so all I really had to do was put the TV in and then put the smoked plexi in front of the TV, and that was it.
The sides of the plexiglass are held in place by friction. It probably would've been nice to have some kind of rails on the sides for the plexi to rest on, but remember, I only had 1/8" of free space on either side of the TV, so that wouldn't have worked out very well. Besides, its thick enough plexi that it doesn't bend (it's 1/4"), so having it held by friction works out fine.
The bottom of the plexiglass sits in one of those mirror holder mount things. I'm sure there's a more technical name for it than "mirror holder mount things", but if you look at most bathroom mirrors, it's that ledge-shaped holder that the bottom of the mirror sits in. The top of the plexi then goes behind the marquee bottom (where the speakers are installed), so that prevents the top of the plexi from coming forward. I then have a couple of big padded l-brackets set back a little ways from the marquee bottom / speaker panel that the top of the plexi rests against, and that prevents the top from going backward. Once the plexi is in place, the control panel has a 1" piece of angled plastic attached to the very end that rests up against the plexiglass, and that prevents the plexi from moving anywhere.
If I ever have to remove the plexi, I'll first swing open up the control panel top. Then, I'll lift the plexi straight up (I left enough room on both sides of the bottom mirror mounting rail) so that the bottom clears the mounting rail. Once the plexi has cleared the mounting rail, I'll bring it back down (just in front of the mounting rail) far enough so that the top of it clears the marquee bottom and the L-bracket. Once that's done, it will be completely clear of the cabinet, and I can then remove it.
Mirror mount clip thing to hold the plexi from the bottom (front view).
Marquee bottom and L-bracket where the plexi top rests (font view).