ok, ye of little intelligence, let me spell it out for you:
UNLOCKING- #1 reason to jailbreak, if you travel internationally, it's a must.
Winterboard- I don't use it, but many do.
Intelliscreen- still no answer from Apple for this.
Tethering- unrestricted and very nice.
SSH- don't get me started.
All-data SIM- I'm on a 100% data plan, like when you get one of those USB stick modems. There's a SIM card inside, pop it out and into the iPhone= superfast...