Well, it all depends on what you want the jailbreak for. For me, being able to actually use the lockscreen for useful information (calendar, emails, txt, notifications) is a killer I couldn't be without (try Lockinfo). Another great solution is MobileNotifier, beta version 5 is infinitely better than Apple's broken solution. A third app I use constantly is SBSettings.
I don't care about themes, but the three apps above are extremely meaningful enhancements to the OS, which I'm not sure if I could be without.
I doubt that Apple will implement SBSetting soon, but it is rumoured to revamp the notification system (the author of MobilieNotifier has withdrawn from the project for unknown reasons, but he says we should expect exciting news soon). If the lockscreen is revamped as well, I might consider running a stock OS (it's a minor hassle to jailbreak every time an OS comes out).