Have been testing a set of insoles from Archmolds from the crew at Runningfree.com. So far have put in about 400km of offroad mileage on them. When it comes to mountain biking shoes they definetly help. Especially when it's tough to make stiff soled shoes comfortable for long periods of time.
So far they have been comfortable and had no annoying irritation to date. They fit into my shoes with only the standard trim. One good thing is that the insoles do increase the stiffness of my shoes which when trying to waste less energy on a 5 hour ride is important.
Next phase of testing will be to see what happens in winter. I ride year round in some of the toughest conditions at times so we shall se what happens next.