I'm not a big fan myself, but if you're interested in single wall tents, you definitely want to look at the Tarptent products (click on the box in the upper left corner of this page.) They're truly innovative, incredibly light, and have a huge following that can give you very detailed information. I could never develop the "warm fuzzies" for single wall tents, but it's a personal preference as opposed to any objective decision. A lot of people whose opinions I respect use Tarptents very successfully, and the ones I've seen are very well-made.

Condensation is an issue with all tents in the right conditions: wet, humid, when the tent will be buttoned down. With a double wall tent, you can mitigate it under some fair-weather conditions by simply not pitching the fly; with mesh-inner double-wall tents, this does an excellent job of eliminating condensation. You don't have that option with single-wall tents - though in fair conditions, the TarpTents can be opened up enough that condensation is a non-issue (based on what others have said.) I've even experienced condensation under a tarp, when I had closed off the ends to block rain. Condensation, for me, has always been more a function of weather than tent construction.

It would also help to know where you intend to use the tent; in the Ohio valley, where I hike, I prefer the versatility of a double-wall tent because I can leave the fly off when it's hot and humid. If you're hiking in some western regions, this might not be a consideration (again, you'll have to get information from someone who knows that.)

If you're not opposed to double-wall tents, check out the Big Agnes Seedhouse, Emerald Mountain, and Copper Spur series of tents. They are lighter than most other double wall tents, and may fit your needs (no promises, though.) They come close to being as light as the Tarptent Rainbow series (the Tarptent is, I believe still a touch lighter; other Tarptent designs are significantly lighter.)