I don't really use followers unless a quest forces one on me, largely because I prefer to sneak up on my opponents and most of the followers aren't too great at sneaking. Not to mention that they keep bumping me and screw up what I'm doing. I can see how someone playing a mage would want someone keeping the enemies at bay, or how someone that just charges in and engages the enemies head-on would want some backup. Just not my style.

I don't use them not for xp concerns but for the fact that I'm a bit wild in my combat and usually end up killing them. At first I brought lidya along with me everywhere, till the part of the mage quest where you find the ball. I ended up burning her down with the boss, cause she was on the other side and I couldn't see her. Now I tend to just use a flame atronoch. As they're relatively cheap to cast, ranged, and elemental. I tend to use fireball a lot as my go to left hand spell, and it's just easier to have someone that I don't have to worry about killing. It's also a nice side bit that they target guys I can't see/find and when they're surrounded by melee, I can fireball in the middle and heal it.

In New Vegas (which had a better follower system), I kept getting killed trying to go north from Goodsprings. In the end I recruited the little robot and the sniper guy to help me blow through the Cazadores. I needed them then. But in the early days of Skyrim, as much as I needed someone to help, they die too easily to really be good solutions to that problem. Make them essential, and they make sense for low levels (like training wheels). Otherwise like I said, probably not my choice for next time.