Just make sure that you are only installing tweaks and themes that are compatible with iOS5, if you do that, you shouldn't have any problems.
I can only imagine how cool it will be when someone comes out with a tweak that allows Siri to have control over the entire phone, so you can do things like instructing Siri to turn on and off Wifi and bluetooth and anything else..
The day the news broke of a soon to be released JB for the 4s is the day I ordered mine from Verizon. I love that since I restored from a backup of my jailbroken iP4 that most of my settings are already set.
I have rooted and flashed ROM's on 15+ various Android devices. I'm two weeks old on the iPhone 4s. Are there any "must have" reasons to jailbreak, because to be honest I tweaked a lot of Android handsets just to get them running smoothly but that is definitely not a problem with the 4s.