W7 on a UX - how might it be, and how compatible is it likely to be?

I've not used W7 in any level of detail yet - I'm not really the kind of guy who beta's stuff. But what with the hoo-ha about it running on netbooks, I'm wondering if I should keep the year-plus-old UX's around until W7 comes out.

By then they'll be approaching / exceeding two years, which will match the longest period I've kept a personal laptop in at least fifteen years. Being an upper-end model and as such, one of the Made In Japan Sony's, I have no qualms about the hardware lasting that long but how, honestly, is such current netbook-grade hardware actually going to run a brand-new OS?

I was considering making a compromise later this year and maybe buy the lightest-configuration R600, ditch the TT's and use the Tosh's as both the UX and TT replacements. This isn't ideal however - I really like having UX-class machines around.

The reason for hanging onto them of course is just that I haven't really seen any compelling replacements for the UX390/490N. Fully featured machines albeit slow - but faster than the majority of netbooks sold today no doubt, 600 grams with the extended battery, handportable, 5-hour runtime on power saving (with ext batt). The new P doesn't do it for me, especially with the lack of a touchpad or a touchscreen - and I don't really see much else on the horizon.

If I keep the UX's and give up the search for anything else, how is W7 realistically likely to run on them?