I guess for me, it boils down to 2 or 3 main advantages...

1. potential weight savings. It might not actually be lighter in this case but I know it would be in larger planes and I'd kind of like to find a combo that works well.

2. low self-discharge - I can charge the battery a week or two before I fly, and all I'll have to do is check the voltage and go fly. No 're-peaking' like nimh/nicd cells. I am extremely nervous when it comes to onboard batteries going dead so this would sorta put my mind at ease, lol.

3. lack of battery deterioration over time - with the low current draw of servos, a lipo battery is bound to last darn near forever as a receiver pack. Plus I don't have to worry about cycling and what not after so many "top off" charges.

With this in mind, I still don't know if I want to spend the money on it yet. A 1650 JR pack would yield plenty of flight time and I've had great luck with them so far but ... yeah you get the idea. I'm starting to ramble so I'll end here.
-Eric