mSATA SSDs are intended to be used for caching of an HDD so that you can get SSD performance without sacrificing storage. Since you're sticking a 256GB SSD in there (I hope you ordered a 7mm model or it will not fit) there is no need for this. Be sure to make a restore disc set since it will be nice to have should you decide to sell the system in the future.
ThinkPad. I'd look into the T430s. You can pull the optical drive out and stick a 4-cell battery in there and add a slice battery onto the bottom. However even the stock battery gets good life. It is also thin and lightweight. If you can wait a little while the T430u which is even more portable will be coming out.
http://www.lenovo.com/products/us/laptop/thinkpad/t-series/t430s/