Lockline is great. I only had to use them once because I dropped my Motorola V600 so many times that the screen would only flash over and over. I never had any problems with them. The extra money is worth it.
Ah, the one difference I did notice is that there is a $50.00 charge added to your bill if they have to replace your phone, with AT&T, the charge is on $35.00. But the way I see it, $50.00 is better than $300+