I agree with David: The 5-series has really come into its own late in life (it'll be usurped by a new model for the '11 model year, and the new 5-series GT has already debuted those underpinnings).
I found the desing of the original fifth-generation 5-series to be quite unpleasant, what with its big eyelashes, strange hind quarters, and slanted interior styling. But the mid-cycle face-lift that BMW applied starting in the 2008 model year really improved the look of this car in my eyes. And it's very good when a car that drives this nicely is not offensive to look at.
Indeed, as Zenlea pointed out, the 535i handles -- and rides -- incredibly well for a 3700-pound biggish luxury sedan. The steering is very sweet and smooth (not surprising in a Bimmer), and overall the car is a supercomfortable highway (and, one would also assume, autobahn) mile-eater. The 3.0-liter twin-turbocharged I-6 and six-speed stick work well in this application. In BMW's entry-level model, the 1-series, this same powertrain yields a crazy-fast muscle car; the heavier 5-series, on the other hand, comes out of the 300-hp oven as a highly refined automobile that still has plenty of power to get you ahead of fellow motorists -- particularly on the highway, where a downshift isn't usually even necessary. Sure, the extra 60 hp and two cylinders in the 550i are cool, but I'd probably save the nine grand and get the 535i. You even get lovely motor music that nearly equals the song of the 550i's throaty V-8.
Rusty Blackwell, Copy Editor