Okay, I have a 535xiT right now and absolutely love it - even love the new design although I see no compelling reason to upgrade yet.
The trunk space is being embellished a little by BMW in those videos. First, notice the kids bike they squeezed in the back with the suitcases? It had the handle-bars rotated 90 degrees so it would fit. Not exactly something you do when throwing a kids bike in the trunk. And what's the purpose of jokingly leaving the kids BMW pedal car and driving away??? Marketing department take note: that doesn't help illustrate how much room there is, it illustrates how much room there isn't. Oops!?
Also, the two full-size mountain bikes... looks tight, seats are off, front wheel off, is it just me or are the end bars on the grips turned down to fit?
Again, it's a great vehicle and a lot funner to drive than our SUVs we've owned - the trunk space is great, but not as great as a big SUV. Too bad more North Americans don't drive wagons - they truly are the best! (edit: my M3 is the best... the wagon's a close second!!)