I have an NC10, and there are better alternatives now as it's getting a bit long in the tooth!
It only has wireless G, if you want wireless N it's not impossible to upgrade it though, costs about £35 in bits and you have to strip it down somewhat.
The battery life for me is 5 hours, that's with the brightness full, and wifi running all the time. You can get bigger batteries, but I believe they stick out of the bottom more.
It comes with XP, not a problem for me as it's a tool, and XP does me fine. I have a spare Windows 7 32 bit license though thanks to my Uni, so I'm thinking about sticking that on.
The built in speakers are garbage, again these can be upgraded if you really want, but then again it's a netbook, it generally lives on silent.
The keyboard is fantastic, i've not used a better one in a laptop/netbook yet, I can type on this thing faster than on a full sized one.
The screen is very bright and clear, and luckly doesn't come with that shiny covering that laptops seem to favour these days, so you can use it without having to shift around without the light reflecting off it.
The trackpad seems a little small when you first get it, but turn off horizontal scrolling and turn on the thing where you can flick the cursor and it keeps going once you've lifted your finger off, and it's very usable. Just takes some getting used to, I never have a problem with it now.
Apparantly you can upgrade to 2gb of ram, but it dents the battery life so I havn't done it, and it runs photoshop and dreamweaver side by side with no trouble. (Only working with upto 10mb .psd files, but then again it's a netbook.)
You can also upgrade to an SSD, which aparantly works very well, much faster boot times and the battery life is improved. Also makes it slightly quieter.
Hope I've helped! I'll be sticking with the NC10 just for the keyboard, it really is a godsend, and I don't mind modding it if I have to. (No need to so far though. I really do fancy an SSD and an W7 install though.)