Subfloor with Pergo or any of the others isn't much of an issue as they are "floating" floors they aren't connected to the subfloor and you have to use their underlayment for the warrantee to be in effect. The only thing is to make sure that the floor they are going over is fairly flat, fill in low spots and sand down high spots.

 

since he said the house is on a slab and that he wasnt taking the carpet up yet so it doesnt get too cold, im going to assume that the subfloor is the slab.

and if i remember right, its a newer house so there shouldnt be too many inconsistancies in the subfloor that he will have to deal with.

 

I installed Pergo in my kitchen and dining room two years ago. The stuff's great. Still looks new. It wasn't bad installing it, but the total area was about 750 sq. feet. You'll want to get some knee pads for when you're connecting them and adjusting pieces you've cut. My knees were badly bruised after the 10 hours it took me to lay it all. I could have saved myself with a $5 pair of knee pads. It took about two weeks before they felt better (Ibonmykneesjoke).