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Yes, good idea. I haven't use mine yet on my rMBP, but on my son's Ipad got a free replacement unit (refurbished) on month 23 due to an issue with thew screen (started to turn green)
 
The 100% correct answer is:

No, if you have no problems. Yes, it's a life saver if you do have problems.

I rarely have failed to recover the cost of an extended warranty on computers, autos, RVs, etc. I always buy 'em and as a free extra, I get peace of mind.
 
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