A fast drive can make a world of difference. I'm typing this on a 700m(stock drive for now)...great laptop.
If you need a larger drive, check the benchmarks and get the biggest, fastest drive you can find. Last time I researched it the Hitachi 60gb 7200 rpm drives were pretty sweet for the price.
There are some 5400 rpm drives that are about the same speed as some 7200 rpm drives...be sure and check reviews before you assume that one drive is faster than another based on specs alone.
Get the 700m if the price is right...i travel with mine and love it. With the extended battery & wifi turned off, I can watch a movie and still have over half my battery left. It's also nice if you're stuck in coach class....you can actually open your laptop and use it....lol.
Best laptop I've ever had....love the screen, love the size, love the battery life.