Being rather new to this E60 and iDrive (6 months now...LOL) my wif has done nothing but complain about the lack of heat in the passenger side (nothing like my E39) and I have dickered with the settings and have noticed that running on "Auto heat setting"the distribution sucks and have not discovered if there is any way to modify these so called auto settings, what I have noticed is that when I take it off the auto setting the distribution settings I have saved in the idrive will now take effect thus directing more of the heat into the footwell of the passenger compartment.
Thusfar I am assuming this is by BMW "design" but can't say I am a fan of this mentality as on the "auto" settings in my case too much heat is directed to the upper side off the car namely to the windshield rather than to the footwell.
hope this sheds some light on your problem (and mine.../LOL)
Jan/1998 528i, 5 spd manual, black on black non DSP. non-Sport, lowered with KONI FSD & Eibach springs in 2008, SOLD @348Kkms and still going strong.
My previous rides worth mentioning:1970 GTO "The Judge",1985 325e M3lite, Euro BMW +
1998 323Ti, in Munich, Germany on the autobahn for 1 yr
Now back in Halifax, Nova Scotia,via Ottawa Canada.
, my daily driver........now upgraded to a 2004 67Kkms 545i....like the E39 ride better though!