The remake, though short, is worth it alone. Throw in Rondo and SotN and you've got portable bliss.
First, the remake feels a bit stiff. Richter and Maria in the 2.5d version feel as if they move a bit slowly. Alucard in SotN feels a lot better to move around with. To be quite frank, its not really much of a problem. The game still plays well but there's simply that feeling that it could've felt a lot better if Richter was more spritely.
Second, the lack of special moves hurt. Fans of the old games can't help but feel limited in their capabilities. Simon Belmont was already doing all sorts of fancy stuff with his whip way back in the SNES. As it stands, with only a forward attack, Richter's whipping is really limited. Understandably though, the remake is probably trying to be as close to the original as possible (paradox). Giving new moves to Richter and Maria would've probably made the game easier.
Third is the visuals. Don't get me wrong, the game looks fantastic. The game looks great and there's a great attention even to the minor details. However, some enemy projectiles are a tad hard to see against the backgrounds. Maybe its just me but it can lead to a bit of an eyestrain every now and then.
Fourth, which is minor, is the voice acting. Richter sounds pretty bad in English while Maria doesn't sound too well either in Japanese. Still, having the option to switch between Japanese and English voice acting is great. The funny thing here is, a lot of people would probably be disappointed that the "So bad its good" dialogue in SotN has been replaced with a smoother translation.
As for what's good, gameplay is definitely topnotch, although it could be harder or easier, depending on your point of view. Players will find themselves dying at certain parts over and over until they figure out what to do, such as during the fights against Death or Dracula's true form. Once you do learn the patterns, it doesn't take much to beat them. Anyway, all the great bits of old school game play are still here. And as already said, as movement is a bit stiff, some of the jumping might be a bit troublesome. Players take note.
As for the music, the musical score is great too. Finding hidden tracks throughout allows you assign which pieces play in which stage. I just wish there was more brand new original tunes. I like Bloody Tears as much as the next Castlevania fan but after at least half a dozen remixes, it gets a bit tiresome (heresy!).
As for Rondo, those who missed it when it came out in the PC Engine can finally check it out which is a definite plus. As for SotN, its still a damned great game and now, its portable. Too bad the extra areas in the Saturn version aren't here though. And unfortunately, there's some slow down on both games.
That said, the compilation makes for a great time. Despite the relatively short length of the 3 games combined (I'm serious. Try finding speed runs of Rondo and SotN and you'll know what I mean [or maybe I'm just greedy]), there's still a lot of incentive to replay, specially with SotN. Any fan of the old games, someone wanting to play a great platformer, or heck anyone who wants to play a good game in general should definitely check Dracula X Chronicles out.