http://www.skyrimnexus.com/downloads/file.php?id=1374
Heh, Dead Thrall summoning level cap removed. That should be fun to play with. Horribly overpowered of course, but it isn't like Dremora Lords aren't anyway.
Messed around a bit with this. With Dead Thrall it both removes the level cap and makes it work on non-humanoids. Only tried it with Giants and Mammoths so far, and both can be necro'd and used to certain effectiveness.
As you might expect, they can't follow you into cities or dungeons; those two in particular seem to function similarly to horses in that they'll still be waiting for you when you go back to the open world. Obviously this limits your summoning/necroing inside if you intend to keep them, but at least with Giants/Mammoths it's easy enough to find new ones. They also seem to fast travel with you just fine otherwise, tagging along with your horse.
I have to imagine the dungeon/city limitation is related to their huge size rather than the mod bypass. Certainly in dungeons they wouldn't get very far.

A zombie of another high-level character who is more regularly sized (Master Vampire, Draugr Overlord etc) should potentially be able to follow you around normally. Though right now there's an unfortunate issue with Dead Thralls randomly disappearing on you anyway after a loading screen, with or without a mod.
Outside the Mammoths and Giants tend to lag behind when you sprint off but they'll catch up, and they hit as hard as you'd expect. In combat they seem to function just like any other melee zombie, becoming aggressive when they sense an enemy and going to town. The appropriate perks seem to work.
I Dead Thrall'd two Mammoths and we took out a couple Mammoth camps. Didn't feel bad about it. At one point it was the two Mammoth zombies and myself fighting against a few bandits who happened to be in the area, and two pairs of Mammoths and Giants at the camp we were attacking. Just a crazy free for all. I was hoping a dragon would show up but no such luck.
As far as stability, I haven't played with it extensively yet but in my stint it was solid enough. No crashes or anything too out of the norm. This sort of mod will be much better when the game is more appropriately balanced with other things in the future, but it should be fun to play around with as it is.