I recently upgraded the vintage-in-a-bad-way wheels on my vintage-in-a-good-way bike. I went from 36-spoke boat anchors to much lighter Velocity A23's with a 24/28 spoke count on nice hubs. The bike feels much more willing to get going from a stop, feels both more lively and more solidly planted on the ground, especially in corners--it's been delightful. I can't say what is due to the lighter weight, or lower spoke count, or wider rim, or better hubs, but at least when you're making a pretty drastic change like I was, new wheels can have a huge difference in how your bike feels and performs.