A few things on the original Rondo that I noticed. Though it seems like it's a port over an emulation IMHO, there's some flaws.
-Some backgrounds noticably (but slightly) darken when they're scrolling. Since I tend to blaze through Castlevania games all the time, I find it barely noticable.
-Besides the rescue cutscenes, the cutscenes' sound are slightly out of sync. Why? Not an emulation problem, but a PSP loading problem. The video starts, then you hear the UMD spin up. Makes the cutscenes off by about a second. But hey, the emulated versions we've been playing for years aren't much better. You can also notice about half a second of silence before each level (even in the remake and SOTN), before the music starts. Nothing big.
Other than that, I absolutely love what they did with the original Rondo. The voices and new sounds are great. Just don't know why they replaced the voices in the opening cutscene. It's german either way. Copyright issues perhaps?