iOS 4.2 should run on the ipad too by the way. There are much easier methods to remote desktop than citrix on iphone and iPad. I often make customer visits without my laptop now and I just take my iPad with me. I use it mostly for presenting and so i just connect it to the projector and off i go. However, there are time when i need to run a web based app that won't run on my ipad and for this i just remote desktop in to my pc which i leave running at home and run the app on that. The ipad has a big enough screen to do this - not sure about iPhone 4 though. One of my colleagues recently did a week long trip to the US to our corporate HQ and was brave enough to leave his pc at home, taking only his iPad. I don't think i trust it enough for that yet
Still, relying on remote desktop is a bit risky. There are so many things that can go wrong (network connection failure at either end, modem failure at home, pc failure at home).