My house has two kinds of spray insulation -- foam and cellulose. This two-part system was recommended by my insulation contractor as energy efficient and cost effective. It makes sense to me ... the advantages of both types of spray insulation complement each other.
Closed-cell foam insulation is sprayed first, directly against the wall and roof sheathing. It's sprayed an inch thick. This seals all gaps, prevents air infiltration, and is a vapor barrier. The closed-cell foam insulation has a high insulating value, R 7 to an inch. Unfortunately, it is also too expensive to use to fill the entire wall.
Cellulose insulation is used to fill the rest of the wall and ceiling. Cellulose insulation is ground-up newspaper that has been treated for fire prevention and to be unattractive to pests. It's inexpensive but has good insulating properties, with an R value of 3.4 per inch. I noticed right away how good it is at sound insulation. The cellulose was blown in damp so it sticks to the walls. In the cathedral ceiling my contractor used netting to keep the stuff up there.
I like the sprayed insulation in my house. The foam insulation really sealed all the gaps and sticks to everything. It dries hard and strong, so it actually has some structural value. The cellulose adds more insulation and has great sound absorption qualities. I probably paid twice what I would've paid to buy fiberglass and stuff it in the walls, but I got a better insulation job and didn't have to do it myself.