I find them useful uphill. Sort of like a right lane for slower trucks to use on climbs out on the highway.
On a NOL had to bail into a driveway this morning when a bus nearly plowed into the back of me with the driver scowling and mouthing something. Apparently I wasn't climbing fast enough for his liking?... of course as soon as he was passed me he had to slam on the brakes for congestion ahead, but I digress.