I read a lot at the DPreview (digital camera) forums, and here is one thread that discusses service plans from Ritz. One suggestion you could look into is calling your insurance company (home owner's or renter's) and asking them about cost to provide "all risks" insurance in case of theft or breakage (Matt's falling down the canyon cliff). Make sure they know you're not running a photography business (unless you are, of course).
To buy warranty (service plan) or not
I've always been warned away from extended warranties and service plans, and usually don't buy them. I do worry about "what might happen", but IF you are a careful person, and IF you don't live in an especially theft-prone area, then the odds are in YOUR favor. If you read the forums at photo.net and DPreview, most folks are against the plans, but some have bought them and used them happily. It's like buying stocks/bonds/mutual funds -- do what lets you SLEEP at night. Some people can take big risks and sleep soundly, others toss and turn even when their money is in a bank savings account -- do what feels good. If you'd like to put that money towards buying another lens for the XTi instead of the service plan, think positive.
I haven't had to send any of my digital cameras in for repairs, and I haven't dropped them on the floor or down a canyon path. MOST electronics that have a defect will show it before the warranty period is over, but that's not a guarantee -- it's a statistical average.
B&H is used by pro photographers, and has been recommended for years. Beach Camera has good ratings at resellerratings.com and on DPreview, and I've purchased from them without complaint. They will usually offer the lowest price of any "known to be reputable" stores and you can use them to compare to the store you're shopping. Ritz is always on the high end of the price range.
Call your insurance company and see what they say -- might be worth your while.
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