I'm a medium-speed driver; I like to think it's just right. I'm never the fastest or slowest driver on the road and I adjust my speed based on the weather. I drive in the left lane if I'm passing people, but in general on a highway I prefer the middle lane. I'm like the Goldilocks of the highway. But WTF is up with people driving below the speed limit in the left lane??? If you drive slow, it's irritating but technically okay by the law, but stay in the right lane! That's where the slow people belong. It's kind of like not seeding yourself appropriately in a race. Just embrace your speed and drive in the designated lane. Likewise, if you drive 92mph in a 65 zone, don't be in the right lane!
This article by LZ Granderson is very well written and explains why it is so irritating, and why it's not your job to police the road with your own vehicle (unless you're a cop, obviously, because then that is actually your job). He also mentions a few other things that I hate like when people stand on the left on busy escalators.