I agree with most of these comments about improving followers. I really enjoy going adventuring with someone, but half the time they do tend to get in the way and it's like you're always looking out for them. Sometimes they just seem to stand there when you walk off, and you have to go back and get them, (well, it's happened to me once!). I've killed Lydia accidentally a few times because she runs into my line of sight just as I fire off an arrow or perform a Shout, so ordering them to stay back and attack using ranged weapons would be useful sometimes.
But the carrying capacity dropping all the time is my biggest bugbear. I'd hoped the Wabbajack "trick" would cure this for Lydia, but it hasn't, and now I can hardly give her anything to carry. Luckily she does tend to equip things if I drop them and ask her to pick them up. (And useful as that is, it's unrealistic, so I think if you do end up over-loading a follower they should start to walk slowly, like you do when carrying too much.)