Once the mod tools get released we will hopefully get some mods to deal with these problems, if Beth doesn't themselves. As it stands with companions it seems like they are a buggy mod themselves, when they are a part of the core game. Shouldn't be like that. I love Skyrim and it's a beautifully crafted game but this is easily my main gripe with it!
Would have also been nice to have more depth to companions, more personality, character related quests etc. Companions really seem just tacked on. And they also render horses useless - how hard would it be to have the option to buy a second horse for your companion, or even have the option for your companion to ride on your horse behind you with some kind of special saddle upgrade?
When they hang around behind me and don't keep up, I like to role-play and think that they are just taking a whizz. When you gotta go, you gotta go.
Hah! I'll have to remember that next time.