I give it a try when I play a new game for the first times, but I usually end up turning it off.

Depends on the game 

Badly done or overdone motion blur can make me feel physically sick. It's not the only offender, and the problem is often caused by an assortment of effects, but motion blur is one of the worst. I've played games that lean heavily on motion blur, to the point that I would get headaches that would completely ruin my entire day. Eternal thanks go out to modders who create plugins to control this "feature".

More developers need to start including options and tools for people to customize their gaming experience. This should be standard by now. The "it should be experienced the way the developers intended" people can take a short walk off a long cat.

I like it. Though, I agree it can be over done. If there's an option, I usually turn it down to a lower level.

Motion blur, DOF, Chromatic Abhoration and similar stuff gets turned off by default if possible.

Heavily depends on implimentation and the game.
Options to turn it off (or down) is always welcome.

Too much is horrible though, its one of those things where "less is more", and only slightly better than none, if done right.
if not implimented well.... it needs to be turned off, or it ruins your gameing experiance.

Yeah i dont really like DOF much either, thats the first thing to go.

not all motion blur is created equal, everybody should watch this video before making up their minds! https://www.youtube.com/watch?v=VXIrSTMgJ9s

that said most mb I've encountered in the games I play is bad and I would reduce it or turn it off, yet there is good mb

I don't mind it on lower settings, Too much of it can affect the appeal to me.

Isn't motion blur used to hide lower framerate? So by logic it means that if you turn it off the game taxes your hardware more?

Subtle per object motion blur is dandy. Screen blur (not for DOF), not so much.