I used a Moss tent that I mooched from a friend last summer. It was pretty good and light and roomy for one - possible, but tight for two.
You know, though, I am wondering about the true need of a full fledged tent. I am thinking about just carrying a big tarp and some rope, and rigging up a shelter. 80% of the time, you don't need a shelter. For the other 20%. I think a tarpeline lean-two would work.
Has anybody tried using a simple tarp instead of a pre-fab tent with poles?