Both my wife and I have one (hers is the non-Surf with a webcam). I use 3 2GB SD cards for storing music, RPG stuff, and church stuff (1 for each). Using synaptic has proven very handy, and I love the resources at
EeeUser.com » ASUS Eee PC 701, Eee PC 900 Blog Forum Wiki Community. I use this as a souped up PDA. I can do a lot with it, and I do, but for anything heavy, I will tend to switch to my desktop.
I would say that it is far from useless. I used it while updating my church's website last week. I use it as a portable bible (using GnomeSword), and it is MUCH easier to carry to Panera than a regular laptop.
EeeUser.com » ASUS Eee PC 701, Eee PC 900 Blog Forum Wiki Community can give you an excellent idea of the wide variety of programs people are running on it.