It's not good, it's great. I'm a strong believer in GSP.
It's more than a warranty or insurance. Non-contact phones are available in 1 or 2 year plans, which covers you against accidental damage, normal wear and tear, battery replacement...etc. There is no deposit or anything either. When phones start getting carried off contract, the manufacturer usually doesn't care if the phone is fixable or not. So you won't have to worry about getting a refurbished or repaired phone, you'll get hooked up with a new one right out of the drawer. Then your old phone gets wiped, and PRC'd. Never re-sold.
Buying the plans with contract phones is even better, because you get the trade-in plus program for free. You also get a loaner phone if it needs to be serviced, and you can pay for it monthly which you can cancel at any time.
Remember that Best Buy Mobile doesn't work on commission either, so if you're offered the plan, it's because it's actually believed it'll work for you.