The SSd technology is still very new and it's only with Windows 7 and the incorporation of the TRIM command SSDs will have a standardized way of combating slowness creep.
Existing products vary A LOT in the quality of garbage collection, so frankly, I wouldn't buy anything except the very latest releases, and I wouldn't buy one unless I was planning on running Windows 7 (or some Linux distros also supporting TRIM).
As for cheap netbooks, you are aware some of these claim they have an SSD while really sporting merely a flash disc (much like an USB stick), right?