I installed the Ubuntu 9.10 Netbook Remix release candidate on my new Dell Mini 10v and the wireless didn’t work out of the box. I think this is because there isn’t an open source driver and Ubuntu doesn’t ship with proprietary drivers installed. Now the 9.10 has been released this problem may have disappeared, but in case anyone else sees this, the way to solve it is to install the proprietary wireless driver (Broadcom STA) yourself.
This is pretty easy using the Ubuntu restricted drivers tools: Ubuntu Menu -> System -> Hardware Drivers (in the 2nd box of applications). Note that you’ll need an Internet connection to actually install this so hopefully you can make use of a wired connection temporarily! When I initially installed this driver there were actually two to choose from but it was the Broadcom STA driver that worked. Now I only see a single option available.