The changes are going into the 2011 328i and 335i. They go on sale in the spring and pricing hasn't been announced yet.

The new engine is coming to the 335i. It's a turbocharged, all-aluminum, 3-liter in-line six that produces 300 horsepower. The new engine, designated the N55, is the first BMW in-line-6 to combine turbocharging, direct fuel injection, and Valvetronic variable intake technology.
Like its predecessor, the engine is a short block, but is quicker, more fuel efficient, and cleaner-running. It still comes with a six-speed manual transmission.
The six-speed Steptronic automatic is optional and how has “pull-style” shift paddles on the steering wheel. The lights -- both front and rear -- change too: BMW has designed in new headlight and taillight detail, and changed the exterior mirrors.  These unique design elements reflect the sporty character of the car. There is a new long hood and a widened kidney-shaped grille.
The 3 Series coupe and convertible come standard in the U.S. with xenon headlights, accented by BMW's signature corona light rings.  At the top, the new headlights merge into a trim bar cutting off the light beam to create that concentrated, focused look typical of a genuine BMW. The corona rings, now powered by super-bright LED light sources, can serve as daytime running lights if that feature is activated. The exterior mirrors also receive a new design.
(Source: USA Today)