I've found that all of their car care chemicals/products have performed exactly as advertised. Their Interior Cleaner, Vinyl/Rubber Cleaner, Car Wash, Wheel Cleaner, and Machine Polishes have all done a great job for me. Others here rag on their polishes, but I've always gotten great results using them.
As far as buying hardware, yes their prices are higher, but the no-question guarantee is certainly reassuring to have. My wife bought me the Porter Cable polisher from the catalog about 8 years ago. Since then I've worn the velcro off of two backing plates (and have almost killed the third). Each time, I simply call Griot's Garage, and they send a new one. No questions.
Pricey? Yes, for some things.
Great service & stand behind the products they sell? Absolutely.