There is no 4.1 for the iPad, and 4.2.1 is a pain to jailbreak (tethered to PC/Mac). My advice it to wait a little longer for iOS 4.3 and the un-tethered jailbrake to come out. I'm running iOS4.3b2 and it is much more stable than 4.2.1 ever was.
Besides the iPad with 3.2.2, and a good jailbreak has all the features of 4.2.1 and many more that are not even available in 4.3. Why bother, unless you have one of those must have apps that requires 4.x or more to use.
