Having spent hours tinkering with getting Ubuntu's wireless to work on at least three previous Thinkpads, before I bought this Vostro I did some research around the internet. I found a bunch of happy Vostro 1400 Ubuntu 8.04 users, and the fact that Dell was releasing Ubuntu on some of its other machines. Good signs. However it seems that the hardware specs between Vostro 1400s vary depending on where and when they're manufactured, so I think that research might have been misleading.
Anyway, I've been trying to get wireless working on and off for the last 3 or 4 weeks, and I'm almost there, so I thought I'd share my experiences.