What I can tell you is that its definatly worth while to upgrade to 3.1 roms.
First of all its not nearly as slow as 3.0 was and has a better interface. Coupled with OS3.9 you will love the "new" look that it gives you. OS3.5 is not worth it unless you can find it cheep. I'm using it and it works fine for me but if you dont have it already go for the 3.9. It will also suport your accelerator better then what you are using now and alow you to use larger hard drives (over 4 gig)