My personal choice and I've been eying it since January is the ASUS Eee Slate EP121. i5 processor (what kills the competition), windows 7 (home premium though which you can upgrade), 64 GB SSD, it's definitely one of the more powerful tablets on the market.
I am using an EP121 with the 128 SSD. As you say, very good, not underpowered like most tablets. I did Windows Anytime Upgrade to get Win 7 Pro -- very easy. Unfortunately, the battery life is pathetic, under 3 hours. The battery is wired in, can't be swapped out. So for most of the work day, I'm plugged in.
