I purchased a 7 year/70,000 mile Subaru Warranty from the dealer when I purchased my 2011 Subaru Outback Limited. After having the vehicle for 2 years I traded the vehicle in on something else and now am in the process of trying to get a refund for the unused portion of the Warranty. They promised I could receive a refund for the unused portion if I did not keep the vehicle for 7 years or 70,000 miles. So far, this has not been an easy process and I have been waiting 2 months to get a refund.
One thing I have gathered from this forum is that major Subaru issues start occurring after 8 years or 100,000 miles, whichever comes first. The maximum length warranty Subaru offers is for 7 years or 100,000 miles. If Subaru wasn't making money on these things, they wouldn't be selling them at the price offered. You have to realize, that the vehicle comes with a 3 year, 36,000 mile bumper-to-bumper warranty and a 5 year, 60,000 mile power train warranty. Any major issue will no doubt involve the power train, so the extended warranty really only covers 2 years and 40,000 miles (if you put on 100,000 miles in 7 years). In the meantime, Subaru has your warranty money to invest free of charge as you pay that to them up front.
Most peoples needs change and they tend to trade their vehicles within a 5 year period. In my case, I thought I would keep the vehicle for 7 years but did not like it well enough to keep it past 2 years.
If you want "Peace of Mind" go ahead and buy it. Otherwise, I would pass it by as Subaru's tend to be one of the most reliable vehicles on the road and that is probably why you bought it in the first place.
Aftermarket companies offer coverages to 130/150k miles. Any extended coverage depends on how long you intend to keep it. $0 deductible is good if anything should happen. Again, aftermarket purchases have the same options. The dealers use the same companies you can deal with directly, so keep this in mind.
Another serious consideration is that if a problem develops and you expect warranty coverage, you will need to produce a proof of scheduled maintenance. In principle, you can DIY and keep a log, but in practice, it works much easier if you keep taking it to the shop and have receipts. The 30K/60K services are a major money maker for dealers and independent shops alike and you know how much they charge. So budget extra 2x the warranty cost if you want no hassles when using it. I'd say, at that point it looks like it's cheaper to lease.
Unless you are buying a German car, there seems to be little need for an extended warranty. Put the $900 in the bank, and if you never have any problems in the first 7 years, then you have a nice little nest egg.
Very rarely are extended warranties a good idea, especially with a car like the Legacy, which has such a good reliability record.
Oh, and Congratulations on your new Legacy. Hope you enjoy it. Right now, I am planning on a Legacy for my next car.