I got it last night. So far, I've only played through some of Metal Slug X (which is, reputedly, one of the better-running games on the compilation). Hard Mode seriously whipped me around with 20 continues, so I only got close to the end of Stage 5. But what I've seen so far, compared to what I remember of the arcade version (which I pumped a lot of tokens into, back in the day):
- There is split second loading when switching characters. The way it flashes dark for a split second every three or four switches can be annoying, but not really game-breaking.
- Using at least an S-Video connection, the game looks sharp. I need to look closer at the screen, but at least from where I was sitting, it appears the graphics received a straight 2x scale-up (which I prefer, as I like seeing pixel edges on 2D games, as opposed to composite-quality blurriness). That's what results in those black-borders on the edges of the screen, though, which some people are complaining about. (The screen still appears to be running at a higher-res, though, as you can see from the menu when you pause the game.) Again, though, this is stuff on which I need to look closer, so don't quote me on this just yet.
- The game seems to run a bit smoother than it did in the arcades. By that, I mean that it runs at the same framerate, but there doesn't appear to be as much slowdown. On more powerful hardware, though, that's expected.
- There is some loading when transitioning between stage sections (i.e. in Metal Slug X stage 2, when entering the pyramid, or when going into the second part of it). It does take a few seconds, but the music keeps playing here (as well as in other loading sections, even in the anthology menu) -- so along with the way the game originally fades to black in those sections anyway, those loading parts do have some decent flow.
- End-of-stage loading sequences, not so much. The screen doesn't quite fade to black before putting up the "Loading..." word, and the last drumbeat in the song seems a bit cut-off. Loading here also does seem take a bit longer at times (which might be expected, if it has more to load than just the next stage section).
- The music doesn't quite loop in the right place in Stage 3. It at least stays correctly on-beat, and you might not quite mind it in heavy battle -- but it's something you will eventually notice.
- There was some split-second loading, maybe about halfway or 2/3 of the way through Stage 4. Didn't darken the screen, though. (Maybe it was there because it's all one long stage without sections. That might also explain why the loading before the stage seemed a bit longer.)
- The game won't go into attract mode until you've spent all your credits; it'll just stay at the game-select 30-second countdown timer. And once you do run out of credits, to get more, you'll need to exit back to the menu and reselect the game.
- The full high-score table isn't saved. Only your highest score is saved in the main Anthology menu, and without initials. When you re-enter a game, you'll see that the high-score isn't recorded within the game itself; the high-score table within the game is reset every time you exit the game.
- As an aside, there are no extras on the DVD itself when you put it into the computer.
Other than that, it's the full-on experience, with nothing seeming to be cut. The programmers even ported the Neo-Geo Giga Power screen during attract mode. [Is it just me, though, or does attract mode loop on Metal Slug X a little more rapidly? Might just be me, especially since I'm in front of a TV focusing my attention on it, instead of being in an arcade with lots of other games.]
Given the flaws so far, it stands to reason why arcade purists are complaining loudly at this collection. But, even with everything described above, I still really enjoyed playing the game.
Later on, I might see how Metal Slug 3 through 6 were ported, since reportedly those games aren't as smooth with the loading. Here's also where folks start to compare with the single/double game PS2/XBox ports.
[One final note -- there's some misconception that these games are being emulated. There might be filenames on the disc that make it look like such -- but given the above-described behavior, these are ports.]
ing happy that they [allegedy] didn't 
