In reply to happy_c: I've never got on that great with them, I think lots of practice and patience is a prerequisite for getting any enjoyment/sleep with them.
Having said that I can see the attraction and I can see if you were proficient at putting it up in a variety of different ways it would be a nice way to camp.
The differences you'll get with a bought one is that it will be lighter, the fabric might tension better and there will be eyelets in sensible places. Try looking at the alp kit ones as a starting point.
Ben