I have 1-speed intermittent rear wipers right now... well for 13-years driving through Buffalo a lot of that time and even then I honestly did not use them that much. Driving into the rain on your front windshield is a different story than rain falling on your rear, more vertical window that you peek at maybe 10% of the time. Variable intermittent speeds would be useless in my opinion. Just one more thing to go wrong.

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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