There is no early payment penalty, but it is advisable to keep the loan for 6 months with BMWFS. I believe the dealer may lose the credit money that they pass on to you otherwise.
Don't forget BMW Ultimate Drive App Credit of $300 and Loyalty of $750 (both if you qualify). I believe the PenFed rate still comes out on top, but if you have multiple incentives from BWWFS then the difference between the two becomes much smaller.
2005 330i ZHP
2014 328d xDrive Sports Wagon (ED 7/'14)
2013 X1 sDrive28i
2013 X5 xDrive35d
2009 MINI Cooper