In my experiences:
1. No, never leaks, in fact I've heard of some dealers putting a water hose in the 7 inch gap between the two seals that seal the roof and running it with no leaks. As far as setting it up, it'd have to be one heck of a rainfall to get any water in your trailer as the main box is protected by the rear section still as the front section is put up, and when raising the rear section up, it's closing the gap not allowing rain water to get in the trailer.
2. Nope, the process they use is extremely durable, Mine's almost 17 years old now, and it's got none of those problems.
3. Don't know, never saw a Hi-Lo up close before, but as the two beds, or bed and slide go out, it creates more living area than you would get with a Hi-Lo.
4. Yup, they sure do. I've not heard of anyone with problems with them before. Matter of fact on an extremely windy day, you don't even get a draft from that either.
5. Chuckle.........(Many on this board know how much I know about all that) But simply put, no, they don't use a lot of wood in them anymore, most of the framing structure is aluminum tubing 1"x1", but mostly it's styrofoam sandwiched in between aluminum sheeting. The advantage of this is simple, stuff doesn't rot, and it provides EXCELLENT insulation. Basically, the framing is around the windows, vents, and outter edges, but that's about it. If you're curious and want to see what I've been through with mine, you can click the link below:
http://members.aol.com/br768
Hope this helps!
[glow=red,2,300]Happytrails.......[/glow]