The latest maps from navteq (what BMW and other companies use) aren't necessarily accurate... even the latest one would tell me to get off this ramp and make a left when you can't make lefts there,... you're supposed to get off at the next exit which lets you go in that direction. Navigation failure. But I'll say that having a dynamic map with traffic info still helps a great deal. I don't know how good the garmin devices are with accuracy...

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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