I would (and did) go with the Thinkpad X220 over both the Vaio and MBP 13. The X220 offers better battery life with the optional 9 cell, a IPS LED screen with better color accuracy and viewing angles than the other two, and is very reasonably priced given it's specs.
Lenovo - Laptop computers - ThinkPad X220
I recommended going with the $855 model and adding the Premium LCD display (that is the IPS screen I mentioned earlier), the 9 cell battery, the free upgrade to the Intel Centrino Wireless-N 100 wifi card, as well as any extras you want like Bluetooth or a webcam. You can also save $50 by changing the OS to Windows 7 Home Premium provided you do not need any features exclusive to 7 Pro.