Sonic CD initial impressions:
Title screen music is always JP even if you set the audio to US. (EDIT: Unless you go to the selection screen and then cancel out. Then it'll change to US, if that's what you've got set.)
Music does indeed seem to be in a lossy format, but it sounds decent. At a guess I'd say probably ogg, given that the video files are ogv.
(Speaking of the video files, I won't have to go to YouTube if I want to watch the Good Ending.)
When I opened the ogv file, it played the JP audio; I didn't think to check whether it's actually a dual-audio file but it probably is. (Otherwise, that would mean that when you select US audio in-game, it grabs the audio from some other file and ignores the audio output of the ogv file.) (EDIT: Yeah, dual-audio OGV.)
The JP audio is missing the lyrics. Assume this is due to some kind of rights SNAFU and not just the fact that "toot-toot Sonic warrior" is a hilariously bad lyric.
So far my "just blow through it and don't worry about making a good future" strategy is much more enjoyable than playing the game the "right" way. But the stages DO seem shorter.
The controls on the Special Stages seem much more precise than I remember them being. If this keeps up, I may be able to get the good ending WITHOUT fucking around in the past.
If I could ever get to the end of a level with 50 rings, that is. Which brings me to something I'd forgotten about until reading the TSSZ review: the level design on this game is FUCKING EVIL. First thing I did on Collision Chaos? Run headlong into spikes and die. Because that's how the level starts out: straight line to spikes, without so much as a single ring in-between to prevent you from dying. And the rest of the zone is much the same: springs that launch you directly into spikes.
Minor things: it's now "Sonic got through Zone 1", not "Act 1". And you can't move until after the act intro border goes away (I thought you could in the original but maybe I'm thinking of Sonic 3).
Oh, and the graphics look GOOD. There are 3 filters, sharp, smooth, and something called "nostalgia" for some reason; that's the one I'm using and whatever the hell it does, it works. The graphics look crisp but not as jaggy as you'd expect from a 16-bit game upscaled to HD on an LCD screen.
While Sonic Generations works just fine with my Cordless Rumblepad 2 out of the box (some rendering problems on the config screen aside), Sonic CD uses that Xinput dickery. So I had to stick x360ce in the folder.
And here's something else I'm finding out about games that use xinput: they apparently tend not to do so well if you've got more than one controller plugged in. I've got a handful of controllers; for some damn reason the one I use primarily is registered as Controller #2. (Logitech has a utility for remapping Windows's controller numbering; it doesn't really work consistently.) And programs that use xinput seem to want to use Controller #1, regardless of which one you've actually set up with x360ce. I had to edit a conf file to get Ghostbusters to use controller 2 instead of 1, and couldn't find any such file with Sonic CD -- so I had to disconnect the first controller entirely to get it to work with #2. Shit like this is, of course, one of the major disadvantages, if not THE major disadvantage, of PC gaming over console gaming -- though of course if you just buy the latest Microsoft hardware like a good little boy, you won't have this problem.
Anyhow, this is really quite a good port and the definitive version of the game. Well worth the $5 even if you already own the game.