are they worth the 500 septims.

they svck, they are weak and always trail like 100 feet behind you when your travelling the land, When I was fighting the twin dragons, he only came after I killed both. Do not buy one. Get a free husky or keep barbas or soemthing...

edit: seems pretty mixed, it's either: they're great! or it's: they're terrible never buy them! guess i will have to buy one.

The poster above is dumb, don't listen to him.

I wouldn't know if they were good in a fight. Every time I get into one, it seems my armored troll in a mile behind me, and then gets lost, and then never comes back. They're REALLY slow.

I agree with this. They are far to slow to be useful and they are not very strong. Might as well pay a follower, they are more useful.

They take up the dog slot, not a follower slot.

At least the dog follows you.

I had no issues with mine, and I didn't regret buying it. They have insanely high health that regenerates at a considerable rate. One of them fought off 4 high level bandits on its own and lost about 1/4 of its health. They're definitely good for support, especially if you have another follower with you as well.

I was thinking more in terms of efficiency, but thanks for letting me know

yeah if you walk in slow-mo every where. I love them but they are way to slow but what do you expect form a troll.

Mine stayed with me.

I think they scale with difficulty. So if you set your game to master and buy one it will have higher stats than if you bought it on novice. I can't confirm this, but I'm pretty sure if you buy one on master and switch your difficulty to say, apprentice, I will keep its master stats.

I dont have a prob with there attack/health or anything like that. When there not 10 miles behind me there awesome. If there was a way to make them faster they would be awesome. I usually just have Serena or one of the Huskies follow me.

Difficulty does not affect companions or summons in any way shape or form. This can give the illusion that the troll is better on Master because it deals 1000000000x more damage than you since it deals regular damage compared to your half damage.

It really depends on the situation on how effective they are. I only take one along if I'm going to be in close quarters, like in a cave or ruin. Their not too useful when your cross-country running, and you leave them in a trail of dust. Like every follower, theres a time and place for each, and advantages and disadvantages to all each.
Warriors are great for up-in-your-face style of fighting, ie caves, ruins and such. Mages are ok for most situations but only with good back up if in a tight area, and Archers are only good in open area, like the tundras around Whiterun.