since I got it, I am voting now. 8/10 for Music 3000. Load of samples, very good new ones, and most samples, inclduing some of the old ones, were re-recorded at higher quality (48 KHz rather than 44.1). They got rid of individual riff volume settings feature (to create fade-in/out effects), but the new system they added, the mixing layer, despite being confusing if you don't follow the in game tutorials, allows much more versatility and should reduce problems encountered by modifying a riff but forgetting to clone it first. The downside of Music 3000 is that it seems to miss all note effects that were present with Music 2000. Yes, you can apply filters on the samples directly, and unlike Music 2000, memory will not get filled with that only one sample, but it will modify the sample across the entire song. There is still pitch bend, note offset and note volume, but no more note pan, note reverb settings (like these red/yellow squares in Music 2000) and the reverb features. Either they got rid of some awesome features, or they made them near impossible to access. Also, the reverb effect that you can apply to the entire song seems to output mono sound now, like the samples. In Music 2000 and MTVMG2 the samples were mono but the reverb was Stereo, which increased the sound quality drastically. Also, like with Music 2000 and MTVMG2, this program can freeze, so save often, and since there were reports about corrupted songs on memory cards I suggest to rename your song everytime you save, so if your current save corrupts then you can try reloading a previous version.
I give it a 8/10, both points being substracted because of the missing features (or their innacessibility), the entire sound being mono and the program being less user friendly in overall than previous versions.