Just to be thorough -

auto-tailgate: opens up to the level you selected in idrive
no auto-tailgate option: it unlocks but does not rise

it's also very testy with the amount of time you have to press it. Either it's not long enough and nothing happens or too long and the alarm goes off. Quite annoying.

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'08 X5 3.0si - Alpine White / Saddle Brown interior
Specs: Sport Pkg, Premium Pkg, Tech Pkg, Comfort Access, Aero Kit, Style 433 staggered 20s on Conti DWS
Mods: Carbon 35 tint, LED angel eyes, GP Thunder 7500k fogs, H&R 20mm/25mm spacers, clear reflectors, gunsmoke-tinted taillights
Coded: Digital speedo, windows/sunroof/tailgate close via keyfob

X5 pics at Flickr