What do you use Telekinesis for? I never had it.
But how useful is it?

I read somewhere that you could throw something like a diamond between some bandits and they would fight to the death over it?

Get the deadly telekInesis mod. Throwing objects at people, depending on velocity can actually seriously harm or kill. The more velocity, the more damage in the mod.

Getting to stuff I can't reach

Decorating my house

But without any mods, if you are playing on a Xbox 360 or PlayStation 3.

Can you decide how to rotate the items or something like that?

You can kill Grelod the Kind with any object you throw at her with Telekinesis.

Never bothered with it in morrowind, oblivion or skyrim. It's a fun little spell, but with so little use that I haven't bothered more than testing it for fun.

The chest where you first meet Katria

Throwing precious gems at beggars as a pastime.

Imagine telekenisis in next gen. Using it to grab trees from the ground as the roots and dirt pick up.

I didn't even know it was in the game I remember I've only ever used it once, in Morrowind - I had to steal something from a Redoran mansion, I think. Never bothered to use it again.

I use Telekinesis mainly to get things out of reach

- Troll skulls used as decoration high up
- Potions some devious game designer put on top of a column
- Stuff behind wooden walls in some places
- Stuff behind metal bars you cannot reach
- Objects on high shelves or ledges in a few locations that you cannot seem to reach any other way
- Stuff that fell behind the furniture and you cannot grab by hand

I will usually try archery first to knock the desired item down or move it, then resort to Telekinesis. I never really used it for stealing or throwing items.

This is my second favorite use of telekinesis.

My favorite use for telekinesis is dragonfly hunting. If you are in the swamp north of morthal, for example, every time you go to catch a dragon fly, you catch one and the other two fly away. Maybe you catch two sometimes. To catch all three, you shout at them and they fall in the water. (Fus, or Clear Skies is good) When they fall under water it's a pain to locate and retrieve them, but if you have telekinesis and scan over the water, you can pick them up quite easily.

Telekinesis can be a good way to cause distraction, and used like throw voice to influence your enemy's position. But I haven't really tried it.

It is also useful for stealing things in stores.

fun and stealing
you can use telekineses to pick up and throw bear traps