I had this dicussion with some techs at my dealership. My 550 heats up really fast and hot, but then again, bmw has had issues of seat heating elements breaking causing seats and cloths to catch on fire or be scorched. My 11 X5 does not heat up nearly as fast and does not get as hot, why I asked, the response was fairly simple, 1) Demographics. BMW has found that a good deal of women drive X5's and when they do when equiped with CW package, they have a tendency to use the heaters all the time. BMW reduced the heat output for the sake of having it on all the time.

As for the temp or speed of warming up. I thing the colder it is, you will notice the temp getting warmer faster just because it is so cold.

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2012 X5 50i ZAP(2VA, 336, 465), ZTP, ZPP, ZPS(6VC), ZCW, ZRC, 322, 4UB, 4NC, 610
2011 ///M3 Silverstone II
2011 X5 50i(lemon)
-- SOLD --
08 550 Msport
07 X5 4.8I sport
04 545i sport
02 4.4i sport
01 540I M/sport
00 SL500
97 SL500