T.F.
We did not have it done, although we have toyed with the idea. I've heard that the spray on is not as good as another type that in nailed in like some type of foil product. I don't know the facts though....
We did, however, completely replace and upgrade the heating/ac furnace and air ducts a couple years ago and we feel like it was completely worth the investment. We built our home in 2000 and the units the builder used were just undersized and we had regular AC bills of $700+ (4000 sq ft) ..we keep ourselves comfortable.
After we re-did all that, my hubby put in about $2000 worth of extra insulation in the attics.
This year, our highest bill SO FAR was $394. We often have the thermostat on 75, I run the washer at least twice a day and dishwasher at least once a day.
We used Collin Air Conditioning in Plano. Brian and his team are great, fair and on time. Very reputable and known in the area.
Hope some of that info helps.