I bought an Acer Aspire One D257 a few months ago. It was f**king slow, upgraded it with 2GB RAM and a 7200rpm Seagate hard drive. Now it's quick enough for normal use as in I don't get impatient. However, the battery life has become rather awful, probably no more than 1,5h of watching videos or doing other cpu consuming tasks. Perhaps upgrading to SSD would solve this problem, I'm pretty sure the hard drive has caused the battery life to suffer.
I'd recommend buying a Netbook with a higher def screen as the usual 1000x800 or whatever it is just isn't good enough. You'll struggle to use Excel, Outlook with a lot of folders and emails is a no-go since there's just not enough room on the screen to display things.
edit: oh, and mine came with Windows 7 Starter, that's also a retarded sysem. For example, you can't change the desktop background. Upgraded to Home Premium.