I had been running an early M400 until recently (it was stolen) I had Vista Business on it with 2GB installed. All in all I was fairly happy with it. Could have been cooler, quieter and a little lighter.. but they were not show stoppers. Was a little dubious about buil quality as the hinge was getting sloppy and a gap was opening up around the clear part of the casing.
I now need to get a replacement ASAP, I was considering the Top of the range M400 but then the R400 caught my eye(entry level one is the same price as the top m400).
I like the idea of the smaller form factor and I think I could live with a usb drive attached. But would I be disappointed with the performance or build of the R400 against the M400 (which was a little flimsy)
If you think I should consider something else please say too :-) I don't want to go heavier than the M400's 2.1Kg either. Usage is primarily note taking + office apps with some coding.