im having some real trouble with pick pocketing in this game.
The fact that 90% chance is the highest it goes to annoys me, and it seems even with 90% chance i get caught 50% of the time.

So it just feels like pickpocketing is pretty useless. any tips on how to do it?

Start by making sure that you're completely hidden. If your skill is still low, only try to steal low weight, high value items like gems and jewelry. It seems like most people at least have a necklace or ring on them. It won't take long for you start cranking up your skill, which will allow you to start going after bigger items.

Also, quicksave/quickload is a pretty nice. It's arguably cheap, but I do it.

I'm really enjoying the skill on my new assassin. I'm almost to the point that I can steal an enemy's weapon from them before combat. The extra carry weight is also pretty nice.

One thing to mention is the more valuable the object the quicker the skill will level. I once pickpocketed Wylandriah's staff and my skill increased by three levels. I've never had any problems with the skill myself, remember though that it's always easier to pickpocket sleeping NPCs. I'm assuming you have the relevant perks of course. When you get the skill high enough nearly all NPCs carry enchanted pieces of jewelry.