From what I hear, MFT seems to be a pain. I don't have it, but about half of the reviews I've read thus far, people complain about it not working (I'm sort of glad I passed on it--I considered it for a while before buying my car, but in the end, it didn't justify the extra $1000+ price increase to me).
Me personally, if I drive the car as much as you do, I'd just get the Powertrain warranty, and not the premium care. If I'm correct, PremiumCare also includes oil changes and general service, which (after I calculated it out later on my 2010 Focus) didn't matter much. I found that I saved only about $100 over the course of about 3 years, which wasn't worth the extra hassle i nthe end.
The warranty that I got for my 2012 Focus only covers the powertrain (engine and trans, and everything enclosed within them). For me, that was the biggest concern. Window motors are cheap. RAdios can be replaced with aftermarket units for $200, etc, so to me, the warranty on the accessories and stuff outside the engine wasn't a big deal to me. And since they don't warrant brakes, tires or batteries. Over the past 10 years, the auto industry has improved most components in cars (it used to be that window motors would only last about 7-10 years, now most people don't need to replace them until 10+ years, unless they abuse them--like trying to roll down a frozen window in winter time).
If you're concerned about your investment, get the warranty. On a car especially, there are a lot of precision-tuned parts that can go wrong. If the car were brand new without any noticable issues, I would say you could probably pass because the mfr warranty should cover anything that comes up early on in the car's life (which from my experience has been the case--any major failures I've had--knock on wood--have happend within the first year or two of owning the car, all while under the factory warranty). But a used car, a warranty may be a good thing, espeically if you don't know anything about the previous owner. The problem that I see with most cars is that for example, you don't know if they raced the thing from day 1, or if they drove it like a racecar from day one (possibly thus causing components to incorrectly seat/break-in), or if they ran it low on oil, or used cheap conventional oil, etc. There are so many variables that you can't confirm with most used cars, so I would probably get the warranty in this case, if you can afford it, in this case. And if it is truely only $1500 for the warranty, it may be worth it, especially as the car begins to accumulate miles (although aside from the trans issues people complain about--and the MFT issues--I'd say that the Ford Focus has been getting better over the years, both in customer ratings, and reliability).