They will be. Using a Mercedes is close enough to using a Buick (I wouldn't go for BMW, but I'll give you more than Kia), that slipping into the other won't be hard. Sure, it handles poorly compared to the Mercedes, various buttons are in different places, it's not as safe to use, and you won't get there as fast, but it doesn't take long to be able to use it well.
LOL- You obviously never had a Mac fanatic be hired, and been totally lost for days, while bitching about the computer that dosen't coddle them like their sainted Macs.
Would you rather hire a driver that learned on a stick shift on winding snowey mountain roads, or one that only knows how to drive a Mercedes on open highway ?