Just upgraded my iPad 1st Gen to 5.1 and jailbreaked. It works like charm.
Tethering jailbreak is not a problem for me since iPad seldom restart.
Following is the link I follow:
The only problem I have is iBook does not work after jailbreak. It can be easily fix by following the instruction below:
I also download the iBook free text book Life on Earth. It is amazing.