Jb'ing is a no-brainer. Why? It allows you to get more than just Apple approved apps. to list a few reasons:
Activator: controlling what happens when you click on your headset, if you have buttons. Adding BT Stack allows you to control your Bt keybaord, even the Fx keys. I love that when my iPad is in its' Convertible Book Jacket, I can control media playback via the sleep button and the volume keys (down-up quickly is next track, up-down quickly is previous track, short hold of sleep button is pause/play).
SBSettings allows me to toggle on/off pretty much anything with a quick slide of the status bar.
For the n00bs: Jailbreaking rarely, and I mean super rarely, results in any actual damage to iPad. As long as you use your head, you can really customize your device to your liking. Whats great is that you can always restore. As long as you ensure that Cydia saves your SHS blobs, you can go to whatever firmware you want. This is key if you choose that 4.0 or whatever it will be called for iPad is for you or not.
I've jailbroken every iPhone (I've had every model) that I bought. Why not take control over something you paid so much for? I paid almost $900 for my ijpad 3G 64GB, so I will make the most of it.
There is almost no contest here. There are several other hacks, tweaks, mods that I have that I did not list, for the sake of keeping this short. But feel free to explore the world of mods for this great device.