I test drove several vehicles, but after driving the 530i, I said to myself "I have got to get me one of these!" While I enjoyed driving the 3 series, the 530i has the interior room to make it a great family sedan, but when I'm alone it is one sweet ride. The 255 HP engine sets the tone, but the car is so quiet and smooth to ride in. I love the idrive. My dealer did a great job walking me through it and now its second nature. I love all of the other gadgets and settings too. I like having an MP3 CD loaded and getting a display of all songs on the idrive display, so I can play them randomly, or dial up some music with the idrive or use the steering wheel mounted controls.
Unquestionably, my favorite feature is the bluetooth capability with my Blackberry. It is awesome. I love calling people hands free - where has this been all my life? The bigger engine is definitely worth it. It makes driving the car very fun. That 550i must be a trip with that bigger engine!
The storage in the dash and console isn't very useful. In particular, the console is very difficult to open and doesn't hold all that much. Side styling is a little boxy. The turn signals are sometimes not easy to disengage.