Mine did trip the CEL, but there was no noticeable effect to the engine running characteristics. There are some horror stories, generally from drivers in northern climates, where all the crankcase oil was pulled through the intake in a matter of 20-30 seconds, but I don't know if they ignored any early symptoms before it happened.

2002 X5 3.0 242,000 miles
2004 325i 107,000 miles