the things that go through my head

There are a lot of cool things you can do with a jailbroken iPhone. The one thing I’ve noticed is that the longer you have your phone without a jailbreak the more you’ll appreciate the jailbreak later on. The iPhone is limited in a lot of different features compared to other phones. When you have had the phone for a while you start to think “I wish I could do this but can’t” that’s when jailbreaking makes sense. There were really cool features released with ios4 that only existed on Cydia (the jailbroken version of the AppStore) before it was released in june and now come default on the phone which is nice. The cool things you can do with a jailbreak are customize your phone,
download and change themes, colors throughout the phone, cool apps that let you control your phone (sbsettings allows you to turn off 3G and location, control brightness without having to go into settings), tweaks like safari downloaded and email attachment saver let you save documents on your phone like a computer and can be managed with iFile. There are other apps that also free your phone: My3G allows you to use FaceTime over 3G and watch youtube videos in wifi quality as well as bypassing the 10mb cap on downloads in iTunes. You can also download paid AppStore apps using a program called installous for free (I don’t use this because I get paranoid when downloading paid apps for free).

The only downside right now is that not all the apps, tweaks, and themes have been updated to work with ios4 and the iPhone 4. Some of them are only compatible with 3.x because the developer hasn’t gotten around to updating their code. Hope this answers some questions, if you have more just ask. (it’s a lot easier to show someone what can be done rather than write about it

Update:

After playing with my phone some other notable apps are Lockinfo that let’s you manage your messages, email, twitter, view missed calls and view events coming up in your calendar.

Also quickreply is pretty cool, it allows you to respond to text messages anywhere on the phone (it’s a little buggy on 4.0 but the basic function still works.) and there are other apps that do this and are a little more advanced and feature rich like bitesms.