I'll agree with Kolla here - I use 3.9 on an 030/50 and an 060/66. Naturally the 060 is faster, but the 030 machine holds its own, and doesn't feel any slower to use than when it had 3.0 on it. It takes longer to boot and takes up more memory, but that's due to extra stuff like Amidock loading at the start. And let's face it, you're probably not going to leave your 3.0/3.1 installation bare...
