Some of the higher priced single wall tents are desinged for mountaineering. The biggest advantage is stability in VERY high winds and steep side walls that shed large amounts of snow. In fact some mountaineering single wall tents that are designed to be used at high altitude assume it is not going to rain (only snow) and are not totally waterproof. Unless you are going to be on a high altitude climb, you can spend much less than the $600 range for a single wall tent suitable for most backpacking.

You should pick up the latest Backpacker Magazine gear review and check out the tents. Do not necessarily pay attention to their recommendations. Rather look at the statistics and find one tha meets your needs.

I guess the first question to ask is do you need a tent at all? I do not use a tent very often in the Sierra - only in mosquito season - otherwise I use a small tarp or bivy sack. I never go into the Wind River Mountains without a tent and a wind-worthy one at that - it can rain every afternoon for days and blow like you would not beleive. In the Cascades, it drizzles and I am not so concerned about wind-worthy but want something with an awning to make camp life easier.

You will probably end up like the rest of us - owners of several tents for varying conditions!