on this, have not had it done, have not talked with any representatives, BUT have done some extensive reading about it.
I have read that its much better than cellose. Cellose is way down the scale on R factor. Cell does pack and does become eneficient.
here is what I have found out. There are two kinds of foam, one that expands to an extent and one that does not expand at all. you want the one that does not expand or put undue pressures on the inner wall of an exterior wall as to causing bowing and pressures outwardly. The process of installation requires that a hole the size of a silver dollar be drilled in the inner walls of exterior walls in the center or each wall stud. that means a hole every 16 inches. the hole is at the very top of the wall ceiling intersection. Once the holes are all drilled out, then a nozzle like a gas pump nozzle is inserted into each hole around the house and filled up from the bottom to the top. When stuff ozzes out of the hole, that particular 16 inch area is done. This stuff will not settle, will not bulge the walls, and will not interfere with the electrics, gas, or piping.
As you are to see, the labor inserting this foam is what makes it soo expensive.
I would really do some indept research on this before I committ. I would see how fast this will pay for itself. I would try to talk to some residents that have had this done. Do not expect this to increase your property value on bit. How many years will this pay for itself in utility savings?
You know what I would do before I committed my self to this expensive process: install storm windows, storm doors, vent my attic, test the effeciency of my HVAC system, caulking and weatherstriping, remember 80% of drafts and leaks are doors and windows, consider addressing the north walls with hard foam insulation boards.
Remember this is what I have read, and what I have considered. No first hand experience.