x220, you need to get an i7 to get a usb3, but the battery life is great, and it's small, and you can upgrade to 16gb ram.
Stick with thinkpad. the 20 series is the last series to offer the classic keyboard. After that, e.g., x230, t430s, you get chiclet keys.
x61, x201, x220. Stick with those. I'd go with x220, but you could even get an x61, and put 8gb of ram in it...it's ddr2 though, so it will be expensive.
Are you sure about this? I have an i7 x220 and it doesn't come with USB3. I think I remember having a tough decision between the x220 (USB2 + nice keyboard) on the x230 (USB3 + chiclet keyboard).
"Three USB ports (of which one is USB 3.0 on the i7 model)"
I would check and make sure that you got one with an i7.