Just a cautionary note that user agents are considered in at least some web dev circles to be
"a complete mess, and near useless" (honestly, read that, it's hilarious too).
Increasingly designers use javascript (jquery framework in particular) to actually sniff features on your browser without recourse to the user agent string, and in fact myself and at least some others are subscribing to the theory that actually, given that the designer marks up his design properly, it should be entirely down to the engineers of a given browser to get it to display correctly -- i.e. engineers building a web browser for small screens should jolly well make sure that valid sites display properly on a small screen.
I'm trying to cut a fairly complex UI issue into very cut and dry categories -- things are still in a real state of flux but I'd suggest that over time the ua string, while it will work on a number of (particularly more mainstream sites) quite well, will eventually become deprecated, so it's not a forever solution.
Ideally there'd be a browser specifically for small screen netbooks that renders pages correctly, of course -- I realise it's frustrating if there isn't.