I never used Odin, don't even know what it is. I just use clockworkmod recovery and rom manager.
Odin is a "one click downloader/flasher" that essentially provides a package deal that has everything you need to flash an upgrade, return it to stock, or unbrick a phone if you mess something up. Each one is specific to what you are trying to install (go back to stock, do an aftermarket ROM, etc).You start the program on a computer, and put the phone in download mode, plug the USB in and once the phone is detected click Start and it does everything for you. In my case, getting it into download mode means pulling the battery, reinstalling it, holding both the up and down volume button simultaneously, and pluging the USB in. This brings up a splash screen with the Android dude shoveling on a construction style sign.
So with my desktop, it took at least 6 hours to do what it needed to do, but you could see the status bar creep forward, and it eventually said "pass" or "succesfully completed". Unfortunately after that it just stuck on the white ATT opening screen. Tried going back to stock but that didn't do any better.
Finally tried it on my laptop, which worked like a charm and installed the ATT Froyo release that will be coming in the near to middle future.
Odin is really cool, and makes me feel a bit better about doing upgrades to my phone. It is a "get out of jail free" card for anything minus actual hardware failure, since it can do its thing from a completely dead/bricked state.