Totally agree with this, the iPad 1 is going to be dead in the water soon, I'm going to miss mine when it's gone, not usually sentimental about tech items, but this was such a game changer.I thought going from the iPad 1 to the iPad 2 was a worthy upgrade, so definitely.
Maybe I'm going to go out on a limb here, but I don't think so. There is enough internal h/w difference between the iPad & iPad 3 that when iOS 6 is announced this summer enough new iOS features will not be compatible with the iPad 1 to make the upgrade value obvious.
We are going to also see a lot more apps launch this summer and fall with requirements for iPad 2 or greater, and not just from Apple. The Photoshop app is just the start.