So it doesn't cure cancer, solve world hunger or even global climate change - but it's still a pretty nice phone!
At first glance, the large, crisp high-res display get's all the Uhs and Ahs, including how snappy the UI responds thanks to the 1Ghz Snapdragon chipset. With its speed and responsiveness, the phone is a pleasure to use! The form-factor is thin, sleek with ergonomically rounded corners and lies well in the palm of ones hand. The teflon coated plastic case gives it a nice high-end feeling texture. The biggest improvement in software features for my use case is the ability to sync multiple accounts for the contacts and the gmail app - now I can get notifications for email arriving on any of my gmail accounts.
My only serious gripe so far is with the placement of the on/off button, which I need to press each time before and after using the phone. Its location at the top edge, is very un-ergonomic for single handed use - i.e. fishing the phone out of the pocket with one hand, turn on the display, balance it on the palm while using the thumb to swipe the unlock pattern and do the basic navigation. I am also not too thrilled about the protruding camera lens and the trackball, which I hardly ever use, distracting from an otherwise very slick and smooth case.
The hardware specs are probably at this point the most impressive of any phone on the market and the Nexus One should be a serious cure for iPhone envy among consumer-smartphone users who for one reason or another don't want to get an iPhone.