How to Enable Alphanumeric Passcode in 2.0
Here's a neat little hidden feature in 2.0. You can use iPhone configuration utility to enable alphanumeric passcodes instead of the usual 4 digit ones.
You just need to email this file to yourself as an attachment and open it on your iPhone. The rest is self explanatory. You may need to right click and "Save as...".
Alphanumeric Passcode Profile
Just so you know, it is going to warn that the profile is unsigned and could be malicious, blah blah blah. If you're neurotic about those types of things, then you can build the config file yourself using iPhone configuration utility, but I guarantee that it's not a virus :).