I have an iXPS2, and i love it. And it's very portable for me; i take it to work and back home EVERYDAY that i work (i haven't not since i've gotten in like a year ago). Not to mention how often i move it around, sometimes i'll have it in the kitchen, other times at my desk, and other times at the coffee table watching TV, and other times in bed.
I could see myself moving to the mobile PC... the ONLY thing that may bother me, is the lack of a case. I know the top is leather, but what about walking in the rain, having it rattle around in the trunk, etc. Although with Dell great CC warranty, that wouldn't be such as big an issue.