Installing SummerBoard will make you unable to sync with iTunes, and will make any music, photos, or videos disappear. The only way to make them show up again is to uninstall SummerBoard.
If you are going to install SummerBoard, install alpha 1.1.1 or older, as any newer version will make your device crash constantly.
For some reason, MobileTerminal doesn't let you log in no matter what.
Python doesn't work on iPod Touch 1 for some reason.
Doom doesn't actually let you play the game. It only shows demo cutscenes.
BeatPhone crashes.
In Labyrinth, the screen sometimes flickers like crazy on an iPod Touch 1.
Any social media apps don't connect to the servers anymore.
The YouTube app doesn't work anymore.
Stocks and Weather also don't work anymore.
Mail doesn't work with any well known email services anymore. Unless you somehow hosted your own mail server, it won't work.
iTunes also doesn't work.
The NES app sometimes crashes (doesn't make it unusable, just very annoying)
iTetris doesn't work right. Try MobileTetrominos instead.
VNotes crashes.
weDict crashes.
I have heard that Widgets has issues on iOS 1.1.x
If you find any issues that I didn't or know a fix for these, send me an email regarding it at adavison512@gmail.com