Should I jailbreak my iPhone 4S

Definitely. As long as you don't go crazy with the theming, there are no cons I can think of. Doing too much will slow it down significantly and cause it to crash sometimes, and that can be annoying. But for a few added functionalities, it'll handle it like a pro, and you'll be hooked.

Good things to install:
Bulletin
NCSettings
Activator

No it's a pain in the arse to keep up with. The different apps are cool but not worth the headache

There is no real reason not to. It's legal. It opens your phone's abilities to what feels like endless customization.... you can even make it operate on other phone's OS's like android or HTC. and the only reason NOT to do it is that it is crashy once in a while and there is a pretty huge learning curve to knowing how to use cydia and all that. that, and if you're REALLY dumb, you could brick your phone out i have HEARD. never known anyone that has bricked their phone by doing it.

take your time learning it. learn ALL about cydia before you start downloading... also pay REAL close attention to all the words on each program's main download screen so you know if there are incompatibilities.

there is also an app you need to download so that if you screw something up, you can go back to this program and it works like a restore point. idk what it's called.

last word of advice, i wouldn't get the free tethering programs. your carrier can notice data usage.

I pretty much jailbroke mine solely for BiteSMS. I have a few other things though. To do things like new sliders and "themes", you need winter board. That shite is a resource hog. I stay away from it.

My3g
Barrel
Fake carrier
Bite SMS- cant explain how awesome it is
Tether me
Pro tube (let's you watch YouTube videos not authorized for mobile)
Tv out tuner (mirrors phone image to tv with proper cable)

That's all I got, I think.