I have a couple of netbooks kicking around, both upgraded to 2GB (the max they can use). The upgrade is absolutely mandatory IMO, so figure that into the actual price. They serve a niche purpose for me as uber-portables that have great battery life and are more-or-less disposable. But while they can run office apps at a passable speed, they are no substitute for the horsepower of a real notebook. I can't imagine trying to earn a living with one except as an interim/emergency machine.

I have noticed that plugging them into an external monitor speeds up their operation somewhat. I imagine updating the built-in display takes a fair bit of internal processing power. Also, disabling the wireless when you're not actually using it saves a lot of battery and increases their performance generally. Wireless connections also suck a lot of processing power.

My policy has been to upgrade when base-level business laptops are being cleared out for $600-700. These seem to stand up much better (even if they're demo models) than the biodegradable consumer cheapies with all the bling. My current machine is an HP -- far from perfect but I tolerate its quirks because I like the keyboard. Given what I'm seeing these days, my next laptop will be an entry-level business Asus or Lenovo.

My 2c.

EDIT: Don't pay too much for a netbook. The last one I picked up (Acer with Win7 starter) was being cleared out at Staples for $147. The memory upgrade (not from Staples) was $30. I bought it to test my current software suite in a Win7 environment, but it's a perfect disposable travelling box as well.