Jailbreaking is great! Until you want to update the iOS to access new features in the new OS. Now, there are other alternatives available on cydia to emulate or add those stock iOS features when the come around, but updating is always an issue.
My iPhone 4 was jailbroken and it was great, I ran custom themes, tweaks and all kinds of goodies. I even dealt with the occasional major glitch that made me have to restore, but it wasn't that hard. It just all came down to wanting to update the OS that is making me not wanting to JB my 4s, especially with the OTA updates.
If you do jailbreak, look at TimelessHD or LiveOS (themes) on cydia, I ran them both and they were awesome.