I finally got around to getting my own copy of this a few days ago.
For someone like myself, a person who really digs these 1980s and early 1990s games, this is worth it. There are a lot of noticeable flaws, but most of them have been described in this thread already and in several reviews on the Web. I think most people here will know what they're getting into. If you feel you can tolerate the flaws, then beneath the surface there's a lot to like.
I've tried all the games at least once now, and a few of them several times. I'll share some quick thoughts, adding onto what has already been said:
Defender and
Joust emulation appear absolutely perfect, as far as I can tell.
Sinistar is also perfectly emulated except for the vertical rescaling (haven't tried the screen resizing code on this one yet).
Wizard of Wor might be perfectly emulated too, but it's been about 20 years since I've seen the actual machine, so my memory is somewhat hazy on that one.
Many of the Atari Games games on here have their sound mangled to some degree. Usually the music or sound effects are slower and lower-pitched.
Klax isn't too bad, but the sound degradation is really noticeable with
Marble Madness,
Gauntlet, and
Paperboy.
I've only tried the screen resizing code on a few games so far, but the results are excellent. Too bad there's no way to save the screen resizing options along with all the other high scores and preferences. You have to enter the code each time. If Midway ever released out a revised version in the future (maybe as a Greatest Hits release), then they should consider making this saveable, and even promote it to a full-fledged option rather than a hidden code. I have no clue why they implemented it as a code, because not only do the games look much better when displayed at one-to-one pixel resolution, but (as Mosaic indicated in his
updated review of this disc) some games even seem to run smoother.
While the low-res games like
Joust and
Gauntlet look weird when stretched, most of the high-res games (which have higher resolution than the PSP) still manage to look reasonably good, even though they're technically being
shrunk to a lower resolution. These include mid to late 1980s Midway games like
Arch Rivals,
Rampage, and
Xenophobe, as well as some of the Atari Games games like
720°,
Championship Sprint,
Paperboy, and
Toobin'.
All three of the
Mortal Kombat games look beautiful on the PSP screen.
Rampart control is slightly better than on the PS2 (which suffered greatly), but still too imprecise to be really playable.
Marble Madness seems to control somewhat worse than on the PS2. I'm inclined to say
720° is a bit worse off compared to PS2, too, but the PS2 implementation of the control was somewhat tricky already.
Toobin' plays well and has responsive control, but as you're playing it vertically-oriented it's a bit tricky to use the arcade-style control scheme (using the four face buttons to move, and either the L or R button to throw cans) unless you can rest the PSP on your lap or the edge of a table. They implemented an alternative movement scheme on the joypad, but it seemed a bit flaky to me--it might be an acquired taste.