Good observation. Actually, many of the soffits have heating ducts. These pictures don't show them. The other thing I wanted to do was keep things symmetrical. They put in these laminate beams (instead of poles). Some of the duct work runs along these beams. If I were to put in put a soffit on one side to hide the duct, when finished, would give the impression that the beam was off centered. I tried to figure out how to resolve this and the only way to do this was to do the other side of the beam. Also, there are is a waste pipe on one end of the room that had to get covered as well. After creating soffits where required, I ended up with several soffits running in parallel to one another, and a few perpendicular. It just didn't look right to me, so I ended up putting in the extras to make it symmetrical. I was also trying to minimize the size of these things, so I was considering double treying the ceilings or potentially doing a coffered ceiling. Now I'm thinking I'll be running crown everywhere, so that should minimize the "substantial" look and soften it up. The ceiling is 9 feet, the soffits are 91" underneath.
The damn laminate beams are 17". Also, I ended up having to cut 5" off length wise on second pieces of the drywall to get the right height. I had some flexibility in the HT room though and made the soffits just shy of 12 inches so I could put two sheets of drywall up without having to worry about cutting them length wise.
Oh, and having to run wires with a million soffits, sure does help.
EDIT: Tim, as far as priorities are concerned... if I made a decision on the projector, it would definately be the other way around. For those big decisions, I like to let things lie until my impatience takes over. I tried to give things time to make an informed decision, get lucky, or a light bulb goes off, sometimes the technology changes things....like the new Mirage screen (do I want to cover my windows now in the HT room)? Or a rumor... Panasonic AE800? For the most part, I plan, plan, plan, then implement. I'm a certified project manager. On this project, for those things I can't plan, I just put them on the back burner until they come to a boil and deal with it then.
In the meantime, I keep my mind off of it by getting covered in fine, white dust.