There is no Boeing procedure (737) I know of to regularly leave the APU running for take-off whereas I understand the 320 normally USES the APU for bleeds. Can a 320 driver tell me at what height it is normally shut down?
My company has both 737's and A320's and we do not leave the APU running on either type. The only exception was on the 737 if we needed to do a bleeds off take off for performance reasons. In that case the packs would be on the APU. On the Airbus we always take off with packs off so there is no need for the APU.
I can't understand DownIn3green's point.