I'll take a stab at some of this, as well. The problem with the CD-ROM file system is just plain ridiculous on MS' part. They STILL haven't fixed it, yet AnyDVD works around it extremely well. Have you ever noticed that when you switch discs in Windows that Windows doesn't necessarily recognize the new disc's name? That's a bug in Windows. (It's actually a lot worse than just not recognizing the name but that's one of the more noticable symptoms). AnyDVD corrects that problem which is why a lot of us recommend always keeping AnyDVD active. It also blocks cd's and dvd's from auto-installing the infamous root kit drm crap on your machine. Excellent!
PIO mode is bad, yes. You always want DMA mode, but, what happens is that if you have a lot of read errors on a particular disc, Windows will drop the DMA mode lower and lower to drop the transfer rate. Well, it doesn't ever change it back! So, eventually with a lot of read errors you'll end up with your drive stuck in PIO mode. AnyDVD apparently prevents that situation from happening? (KUEL! I didn't know about that one, James...very nice!)
And the last is that because AnyDVD hooks into the system at a low level, it is able to do its magic without a lot of resource overhead. The creator of AnyDVD did a remarkable thing. When I first saw it, I was mortified at actually paying for what I considered to be a "simple driver". That misconception is still around today. I couldn't have been more wrong about what AnyDVD is and does. It's NOT a "simple driver" by any means and does a LOT for such a tiny footprint. He should be commended for what he was able to accomplish. AnyDVD is actually very brilliantly written. I'm a software engineer so I can appreciate the talent that went into writing it. Believe me, what he accomplished is NOT easy. All in all Slysoft deserves the money for AnyDVD and CloneDVD IMO. It's WELL earned!