I jailbroke my iPhone about a week ago. I have been really suprised. I found quite a few apps that I could acutally use. While there are quite a few themes, enough to give ” those Bastards from Findland” ( thanks Edward @msmobiles) a run for their money.
The down side of this is that the iPhone becomes unstable.
An example of this is I installed winterboard which is basically a theme app. Winterboard is cool and has some sweet themes, which are very easy to install. But the app seems to reload the theme everytime you go back to the home screen or switch between apps. Since the iPhone wasn’t made to deal with that kind of transition, ocassionally the app will freeze up the iPhone.

Which brings me to the following speculation. I believe that the next Gen iPhone will be even better with jailbreaking. Why? More RAM. With all these memory intensive apps 3.0 and hopefully a new iPhone will be great.