Can you still play roms when you upgrade? Like SNES and GBA games?
also, why can't you just upgrade to 3.02 without downgrading first?
Yes, in fact, you don't have to run devhook anymore to run them. All you have to do is make a GAME150 folder in /PSP and all your emulators will automatically show up in the XMB. Same goes for PSP isos or PSX games. My PSP is getting so much more use nowadays. I'm currently playing Dino Crisis on it as I've never played it before or any other adventure/horror game either. Everything has been going smoothly.
You have to be at 1.50 in order to install 3.02 OE-A. (So, you have to find the appropriate downgrader for your firmware.) Afterwards, you can install 3.02 OE-B. If you're already using the official 3.02 then I'm afraid you can't downgrade to 1.5 at the moment.