If you are looking to boost it later on, and be serious about it, and you don't want a headache, look for a manual GS. I can't think of anything off the top of my head in the GS's you should look for specifically - just check for the usual. It's not like the 3G's had the same infamous crank walk problem as the 1G/2G. Happy hunting!

Here's a link on the 3G forums where the majority of Problem Reports are posted. Hope it helps! http://www.club3g.com/forum/forumdisplay.php?f=113