Well, I just got the preview of mathematica for OSX.
The install was easier than ever... it involved a single drag and drop.
The program itself seems to be a bit faster than it was before. Importing data files from disk seems to have improved. Even some of the calculations that I do seem to be a bit faster. Alas, I have done no quantitative tests and I am afraid that it is possible that in my love for OSX I am seeing the new version with rosy colored glasses.
User input prompts are definitely slower... following with the general malaise that I've seen in OSX with window draws.
I also like that they followed the UNIX/Linux style of not having the kernel open up as a seperate application... it is more or less invisible.
I will soon have a G4 733 w/ 512 RAM to run it on... then maybe i'll really see something!