I'm waiting for a flight to my snowboarding holiday and am enjoying the benefits of true mobile computing - I'm using my Samsung Q1 Ultra PC running Vista (Home Premium) together with my Vodafone "pebble" 3G adaptor (connected via USB) - both are items of beauty.
It's a great experience - I'm using the touch screen of my UMPC to write this. Vista runs really well - it takes three minutes to boot from cold - I tend to use hibernate to cut this to a few seconds.
The combined weight of both devices including the charger is less than a kilogram and I get >3 hours battery life too!
I have my Zune loaded up with movies and music for the flight too so I'm all set :-)