I'm ambivalent about single-wall tents; at least, single-walls such as the Fitzroy, which use a PTFE-based fabric (similar to older Gore-Tex) to create a waterproof-breathable shelter. Some of my reticence has to do with the price, which is a result of the fact that this material is very expensive. Also, such a tent has to be somewhat over-engineered to compensate for the lack of a backup system like that offered by a fly/canopy combo (that said, Bibler's creations are absolutely bomb-proof when it comes to construction). They generally work as billed, keeping condensation to a reasonable minimum. But, when it's cold, a single-wall tent will often be colder than a double-wall tent (no trapped air layer between the two walls) and hotter when the sun is out (ditto).
Setup is another issue. The poles go inside the tent, so on the Fitzroy you have to crawl inside and thread the poles across the tent and into pockets into which the pole ends slot. With practice, it's perfectly doable. But if it's windy and dark, expect some thrashing around before the tent is up.
Finally, there's weight. The Fitzroy sleeps three and weighs just over six pounds, which is not bad. But that's without a vestibule, something most people think of as a key feature for extended mountaineering use. To add the optional vestibule increases the price by $125 and adds over a pound. At that point, you might be better off with a tent such as Marmot's Thor ($449; www.marmot.com), which sleeps two and weighs about eight pounds.
More tents reviewed in Outside's 2004 Buyer's Guide.