After 16 months and 15,000 miles, I'm still happy with my 2011 Fiesta SE with 6 speed auto tran. This was after an 18-year love affair with 1992 Mustang LX 5.0, so you can imagine the culture shock of a 1.6L, 120hp engine.
In almost a year and a half I have had exactly one problem with the Fiesta -- a rear window weatherstripping came loose. The Fiesta is a slug off the line -- 35mpg in town makes up for that -- but once revs build it becomes downright zippy, it holds Interstate speeds just fine, and really likes corners. The auto transmission is quirky but most of the time is fairly smooth. The interior and exterior are in good shape so far. Oh, the clock is 2 minutes slow -- always.
The 35mpg is the best feature, of course, and that's mostly in town. Seating is at least as comfortable as the Mustang and probably better for rear-seat passengers. The handling and steering feel are very sporty and it can be an exhilarating ride on twisty roads. The sedan has a fair-sized trunk (it easily holds our largest suitcase); the fastback is better looking but has very limited cargo space.
I can't think of much to improve on the Fiesta beyond what most reviewers have mentioned -- a few more horses and a smoother automatic transmission. Beyond that it is darned near perfect as a subcompact economy car.
If you are in the market for a subcompact, you owe it to yourself to check out the Fiesta.