If you can go up a little in price, my strong recommendation would be the Lenovo Thinkpad X220 with the IPS display.
- Start here: Link
- Select the IPS display upgrade (listed as "Premium")*
- Select 4GB of RAM (2GB can cause a bottleneck even for daily multitasking) unless you find somewhere to buy an extra 2GB (to upgrade from 2GB to 4GB) stick for less than $49.
- Consider the 9-Cell battery if you want to realize your desire for battery life. Note: sticks out the back.
- Consider the $10 500GB HDD upgrade if it's of benefit to you.
upgrade the processor past the 2520M. You shouldn't need any higher than the base 2450M unless you need VT-d/AES. Prioritize the IPS display and battery upgrades first.
*The IPS display's availability is part of my strong recommendation for the X220 (other half is build quality). The stock display has rather mediocre contrast and overall image quality, but the IPS display is one of the best displays available for an ultraportable. I would not recommend settling for the stock display.