Slow? Everythings slow in Europe due to our PAL TV system. So if you compare the NTSC and PAL version of SNES R-Type III, I wouldn't be suprised if the PAL version runs slower.
PAL makes for example Tekken3 on PSX unplayable in Europe if you're used to the NTSC version. Timing is completely different.
Raylight Studios is located in Italy, so they probably used the PAL version as reference.
As for the music... I think it sounds ok on real hardware.
I just noticed that the "R-Type" I thought I played back in 1992 actually was "Project-X" by Team17 on the Amiga
Which by the way has a lot better music than the boring R-Type tunes.
The port of R-Type III to GBA isn't perfect, but I don't think it's as bad as most of you say either.