Most financial people will tell you to avoid extended warranties. Phones are the one place I make an exception. I've been burned too many times and decided I'm willing to take that chance. It seems phones are becoming less dependable/durable, and I've had problems even web protecting them with cases from day one. With some phones, repairs can be difficult, limiting access to cost effective services.
This is pretty much what happened to me. I had an M8 but the USB port went bad on my first one and the warranty roulette they sent me. The local repair shop couldn't fix the second one because of the phone design, and it was out of warranty with about 6 months left on payments. My only choice was too buy out the contract and upgrade. Verizon was willing to exchange it and let me use the next warranty roulette phone as an early upgrade, but I couldn't wipe my phone to protect my data with a dead battery.
Now that I'm in a G4, I've come to find out it's one of the early batches that could have a hardware failure. I bought the extended warranty on this one so I can make sure I'm covered until I trade in. Would I suggest it to other people? I guess it depends on your history and if you've noticed any common faults being reported on the phone you're looking to buy. I bought it, but with the knowledge that I could loose money on the deal.