I have the brodit passive holder in my car and the zagg shield on the N900. The N900 will not fit into the holder with the full body cover. The side cover parts of the shield interferes with the "holding grip" of the holder, damaging the cover while sliding the N900 into the holder. Also the additional thickness added to the N900 by the zagg back cover will make fitting the N900 to the holder really really tight (too tight IMHO).

I removed all but the screen cover and now it fits really nicely in the holder. Win some, loose some...