I agree with you that the MD-80 is quite a nice aircraft. It rises quickly and quietly. I've been flying on a lot of them, with American of course! American has a lot of MD-80's and they will be around for at least ten more years, if you fly American within the United States chances are it's a Super 80.
That's what I get most of the times I fly from Chicago to NY La Guardia and back (that's what I always do when I to or from from Brussels on a 767), I like the new interiors. I wasn't too crazy of AA's MD-80's but now that they have the new seats, I enjoy flying on them. On some of the Super 80's, the First Class cabin has 20 seats instead of 14. I must say that American is doing an outstanding job in refurbishing the interiors, even in Economy the seats are comfortable and a bit of legroom is added like you said. You're right, now about 50% of the fleet is refurbished, I think that most aircrafts will be refurbished early next year.
Have a nice flight.