I wish iOS made it easier (or possible, w/o a jailbreak) to write system-wide apps like Swype. I wouldn't be surprised to see this ability in future release of the firmware.
Apparently it's in Cydia now, for Apple's apps only.
I jailbroke my ipod touch yesterday and struggled to find anything good. SSH is kinda dull, SBSettings, Adblock and a few other basic things are the most useless and ugliest apps I have. This article does point out a few things - some business, some for iphone/ipad3g, some overpriced. So basically jailbreaking is largely useless on the ipod touch. Unless you want to simulate something from two decades ago.
I'm surprised they didn't mention VLC. Being able to play non H.264 content on my iPad has been great.
After apple released a non-att option, I have lost all my ooph for JBing devices
Did they ever fix the "JBing horks up your notifications part of the time" issue?
Also, there's a beta version of Swype. Kind of wonky, but single finger SMSing is still nice.
If these are the problems you are trying to solve, just don't buy something with iOS on it.