I have had an acer d150 netbook for over a year now. I initially picked it because the keyboard was the best one I could find on a netbook. It has been awesome, and I won't go back to a laptop ever again. I run ubuntu 10.04, and everything worked out of the box. I actually use gnome2, so not that lightweight, but with a single panel and the docbarX app, it's still very nice. Even after a year of heavy use I am still getting 5+ hours of battery from the 6 cell battery.
The screen is just a tad small at 10.1" but the battery life on the slightly bigger, more powerful 11"+ screen netbook/ultrabook is significantly less than what I am able to get.
When I replace this netbook later in the year I will be trying to stay with the acer brand. I will probably move to a 9 cell battery and an ssd to extend the battery to 8+ hours...
Acer seems to consistently have the biggest keyboards in the netbook class. As a fellow vim user I know just how important the keyboard is to the usability, and I think that really should be one of the main factors you use in choosing your netbook. I went to the store and tried out various netbook keyboards to see which was best. I have coded 4+ hours on this netbook with no issues on many occasions.