I've had pretty good success with them, especially on Ants in my yard for a couple of years now. Below is the link to the company that I have used.

Here is a link that might be useful: Nematodes

dao's link is where my nematodes come from. You get best results when the soil is very wet, like from several days of drenching rain.

Otherwise, your pest problems generally go away on an organic program. You will see the return of birds, toads, lizards, and other creatures that will keep your insect population in check.

For bugs that creep into the house, ordinary boric acid dusted at the entry points or where you have seen the bugs will keep your home completely clear. In Texas there is a huge problem with roaches. I have always kept a supply of boric acid in the house to dust into cracks and corners. My house never has roaches. A few years ago we had our house remodeled. They had to open the walls to put in some badly needed insulation. Into each wall cavity I had them drop a teaspoon of boric acid. I don't ever expect to see bugs again. However you cannot use boric acid in the garden. Boron is a trace element needed for plant life but any more than a trace will kill the plant.