I just put those iridium ones in my '06 3.0i @ 143k miles. I've heard you shouldn't gap the iridium but I think they come within spec when ordered so not sure it's needed. There's a DIY thread here I used and plenty of other threads on the subject if you do a search:

http://www.xoutpost.com/bmw-sav-foru...m-bkr6eix.html

Not sure the iridium made a difference in performance/mileage but the plugs I pulled out didn't look too bad. My understanding is iridium are recommended as they can provide both longevity and performance whereas platinum plugs don't perform as well and copper plugs don't last as long. But I'm sure there's a lot of guys that know more about this than me.