I have a Mini 9. It's foolish to buy anything but the base model, unless you want the webcam. Remove two screws, pop off the rear cover, and the memory, SSD, and wireless card are all right there. Takes maybe 5 minutes to upgrade the memory, a bit longer to change the SSD. Mine has been upgraded to 2GB of DDR2, and I'll be going from the 8GB SSD to a 64GB. Because of how easy it is to swap components, I'm holding onto the 8GB for a different OS setup.
A lot of people don't care for the keyboard layout, and while it does slow me down, it's hardly a deal breaker.
What I love about the Mini 9 is the fact it is silent. No fans, no moving parts, no noise. I was worried it would get too hot, but so far it doesn't even come close to what I would call uncomfortable temps. Hell, with winter coming it makes a good lap warmer.