In reply to ablackett:
Yep. Tried and tested in many of Scotland's finest lay-bys. It's a bit more likely to hit you in the face on a windy night than if you put the guy lines out, but generally it holds its shape fine.
We just upgraded to the XL Air version, which has a porch - it's slightly lower than the original, so a bit harder to sit up in, but the porch means the inside doesn't get so wet when you open the door, and there's a place to put shoes. It also holds its shape without pegs, though we've only tested it in the benign climates of the southwestern US