Let me start by saying that I do like this game a lot, but there's some issues that make it hard to recommend.
To those who are unaware, Dreamcast Collection is an oddball series of four great games that all have some element of lazy porting to them. Crazy Taxi is the later version that is missing the original licensed soundtrack and product placement that gave the game its unique and "CRAZY" feel. Sonic Adventure is actually a gimped version of the earlier 2004 PC port Sonic Adventure DX that doesn't even run in widescreen or HD as far as I know, but it's still playable at least. SEGA Bass Fishing I'm not sure about. Apparently they all have issues with their controls too.
However, unlike the other three games, this actually IS a good port, the best of Dreamcast Collection in fact. There's nothing particularly wrong with this port at all as far as I can see. It looks good, runs well and doesn't seem to be missing anything. It's still the same fun, fast and challenging rhythm game it always was back in the day. While it IS the second game in the two-part series, the story is light and the characters are all re-introduced so playing the first SC5 (which hasn't recieved a HD port) isn't required to enjoy this game.
And without a doubt the game itself is a blast! It's a fast-paced rhythm game with cool characters, a fun story and awesome music. The graphics don't exactly hold up well, but they are colourful and aesthetically pleasing, and even though there's only a handful of stages, the gameplay is solid and challenging. I'd definitely recommend it to any SEGA fans out there, even if you generally suck at rhythm games like I do. If you find the collection for cheap, THIS game is worth it alone.
If you can get the game working, that is. Unfortunately, there are some technical issues.
Most importantly, the Steam version of Dreamcast Collection does not configure itself correctly and WILL NOT RUN without registry editing. This is common among all four games in the collection and supposedly is an issue specific to the Steam versions, and they will most likely not run unless you fix the registry entries for each game. After this initial hiccup, you might need to ♥♥♥♥ around with the game settings to get the graphics to even appear. However once the game is properly installed, you won't run into problems like that again.
While a relatively minor issue, the game will also not run in anything higher than 720p, at least not to my knowledge, but honestly, considering the original was designed to run in 480i and 480p, you're not missing much from not being able to run in 1080p. The game still looks pretty fine at 720. The later-released classic SEGA ports like NiGHTS Into Dreams, Jet Set Radio and Sonic Adventure 2 are much more functional ports which run in any resolution and include Steamworks features like cloud saves and achievements, but Dreamcast Collection on PC is incredibly bare bones in comparsion.
Another huge problem is that if your computer is slow the game will be out of sync with the music. Even though you'd be hard pressed to find a computer that can't run a Dreamcast game in this day and age, it's worth nothing that If you have a slow computer, then this game will run slow. Like all of the Dreamcast games on Steam (even the ones after DC Collection), it lacks any frame-skipping at all due to it being originally designed to run on a specific set of hardware, but in a rhythm game this is an incredibly serious problem since the action will desync with the music if the game slows down even slightly. If you have a decent computer, then you won't run into this issue, but I wouldn't bother trying to run this on your $500 netbook or anything.
Technical issues aside, let's talk about the price. $10 is pretty fine for what you're getting here, but it should be noted that for my fellow Australian gamers, in the Australian store this game is one of those that costs twice as much as it should. (always be sure to check www.steamprices.com) At $20USD it's way too overpriced for the amount of content in the game, so get this through GMG instead. At the normal American store price of $10USD it's a little more reasonable.
Actually, consider getting a version that doesn't require Steam, as this game has no Steamworks features whatsoever anyway and you can avoid that registry issue altogether. Better yet, the Xbox 360 or PS3 versions, the Xbox 360 collection disc, or the original games themselves will give you a much smoother experience if that option is available to you. Both Space Channel 5 games are also available on PS2.
But if you can get the game working and can get it on the cheap, then this is a fun and challenging little rhythm game with charming characters and incredible music, so it's probably worth the effort anyway! Overall, it's not bad at $10, but hard to recommend at $20 in Australia, especially considering its short length, the technical issues and lazy porting. I'd be hesitant to give SEGA money for this, but if you want it, then by all means, get it! Just be wary of the technical issues.