Re-enabling it, thankfully, is very easy: Go to Applications → Utilities, ⌘-click Terminal.app and select Get Info (or press ⌘-i) and check the Open in 32-bit mode checkbox. Finally, start Terminal.app and you should have your beloved Visor back.
So, here's some quick information from my latest foray into creating a favicon:
@drewm just tweeted about a very cool free utility for developers called Developer Color Picker (DCP) by Wade Cosgrove, courtesy of Panic (developers of, among others, the excellent Transmit FTP client for OS X that I own and love).
It's easy to get confused as there are several outdated downloads and project pages floating around the web. It appears, however, that this github repository is where Mogenerator is being actively developed.
I can access T-Mobile UK WiFi HotSpots with my T-Mobile Mobile Broadband account (I have a 3G USB stick) but I find the signing in process rather painful. It goes something like this: