Don't count on getting an LCD in exchange, at least not from Best Buy. I had a Best Buy PSP on a 50" Samsung DLP. The set just broke (November), and BB wouldn't even attempt a repair. They just "lemoned" it immediately.
Stores no longer carry them in the 50" size. So all the store wanted to do was give me a $1000 gift card, with the cheapest name brand 52" LCD costing $1600 (so $600 out of pocket). The cheapest name brand 46" was $1300 (so $300 out of pocket). Best Buy refused to switch from DLP to LCD. They said a PSP swap had to be DLP for DLP, LCD for LCD, Plasma for Plasma. If no DLP is available, you get a store credit. They won't give an LCD for a DLP, despite the warranty stating you get a comparable new TV (they claim no comparable set exists any longer).
Best Buy also told me that if the repair cost exceeded 50% of the junk out credit, then they wouldn't even attempt to repair the set. That is why mine was lemoned on repair attempt #1 (diagnosis was that a new light engine was needed). So any light engine replacement is going to cost over 50% of the store credit they would issue you ($1000 in my case, so any repair over $500 parts and labor would result in a lemon on a 50" DLP).
So with their PSP, it essentially will only cover a bulb replacement, color wheel failure, and maybe a digital/analog board failure. Just about anything else, or any combination of two will result in a junk out.
This was a replacement for a set I paid $3600 for about 2.5 years ago. I was only getting $1000 credit today. So if you buy a $1500 DLP now with a PSP, they won't be carrying any DLP's in less than a year. So if your set lemons two years from now, what do you think they are going to give you? Maybe $500 on a gift card towards the purchase of a new LCD?
DLP is dead. A service plan isn't really worth it, at least not at Best Buy. On the larger DLP's, you will pay $300 for a service plan that may net you $500 towards the purchase of a new TV 2-3 years down the road.
DLP = Disposable Light Projection