When I bought this warranty from Microsoft, I was told it also covers all hardware and software issues as well as accidents. I think that's a pretty good warranty. Plus, I can take it right into the Microsoft store.
I thought this was the best way to go as well. I bought my i5 at Staples(since they had a $100 off coupon of a $499+ purchase during back to school days) and I wasn't keen on using SquareTrade. So I went to the Microsoft Store and they had no problems signing me up, even though I didn't buy from them.
In essence all these plans work like insurance. They calculate the expected number of replacements vs cost and profit from the excess. Most likely its not MS actually providing that but someone else and MS is just getting a sliver from the sale. It doesn't really matter one way or the other as long as you get good service. I once worked for an insurance company that provided branded services to Toyota, Honda etc. it was completely run by the Ins co and had the look and feel of the subscriber (Toyota, etc ).
Refurbished devices typically have to comply with regulations and generally would be certified restored as new. On other vendors sites that offer refurbished units for sale they identify units with scratches, dents, blemishes separately. you will also see retailers selling open box units etc. These are NOT refurbished even if they also sell certified refurbished units. They may also use these as store replacements depending on their policies.