Seems to me that interference detection is the main component of Revit that Autodesk market their product on.
Yes, of course it has it's uses, but is it all-important?
My experience with it is that we generally don't use it until late in the piece. And when we do, more often than not it comes up with a schedule of thousands of clashes here there and everywhere, which of course, presents us with a very daunting task!
What I strongly believe the tool does, is put the user in a "I won't worry about co-ordinating stuff as I go....I'll just get as much in the model as possible and use clash detection to co-ordinate later" frame of mind! To me this is unacceptable.
Perhaps what is needed is a "live" clash detection system.....one where an alarm bell rings or an error message appears saying "user note: placing duct here will clash with a beam....do you wish to continue" or something along those lines.
One for the wish list, perhaps.