I'll just put my 5c... I've had an experience dealing with two outside companies. One of them was www.warrantybynet.com
which I'd stay far, far away from. I can write forever what they made me go through. They will make every effort possible to refuse the claim. Their advertizing on their web page is total B/S and they will never share with you that within passed few years they changed their administrator at least three times. Stay away even if it's free, beacause it's not worth your aggravation. Once in my E320 I had to change a head gasket due to the common problem on straight six 3.2 where the oil line is too close to the edge of the head/block and in time oil leaks to the outside of the engine. My MB guy showed them (warrantybynet) TSBs and all other material involving this problem, and after probably "nice" tip they finally approved the repair. (please note, that they will send their inspector to take a look at your car) It took about four days of wasting time and tens of phone calls. Warranty by net wants something from you every single time, perhaps to get you tired. They will never just give you an authorization number an tell you go ahead. The list goes on and on.
The people I'd strongly recommend are www.warrantydirect.com
They have paid over 4.5K in the repairs on my S500. They are so easy to deal with I love them. Just call, tell them what "hurts" and pick up your car from the shop when it's done. Paperwork? What paperwork?! All they want from me is my signature...
The company is based in NY and what's most important they are their own administrator.
Hope this helps a little....