Jack, as a fellow Intercept owner, definitely try to rehabilitate the thing first. Sounds like the biggest thing you need to do is to do a factory wipe and reset. It sounds odd, but the thing behaves like a Windows OS with bitrot after a while and a purge, reset, and repair seems to make it right as rain when it gets twitchy. If you want to upgrade the firmware,
XDA Developers is a good place to start. Personally, I'm running stock Sprint Android 2.2.3 with DL05 baseband, CrappyKernel 1.5, and Zeam Launcher 3.1.10. I'd tried a few additional apps early on in an effort to extend battery life and convenience, but I eventually just stripped them out as they were less help than advantage. (
Original post here.) The only thing I really don't like and never got around to getting to the bottom of is Joseph Mother's Crappy Kernel's permarooted, so it can be a security issue if you're not careful, and there's no support for SD card swap partitions either. Battery life, performance and stability are good, though. Even after I retire it here with the P'tel GSM switch, and being thoroughly underwhelmed with Android on a whole, I still plan to keep it around for odd jobs as an XBMC remote, for Kik/Nimbuzz and e-mail at home, and as a VoIP handset or other
stupid smartphone tricks.
Also, if you're dealing with mail servers that do IMAP4 push and aren't Google, K9 Mail is a far superior mail client to the Android one. If you want to pick my brain on any more technical bits, don't hesitate to ask. :)