I only started running regularly a year back, and I certainly feel something like a long-drawn low-ebbing pleasant kinda 'high' after a run. I also have double the energy now-a-days and am twice as productive since I started running. Concentration has improved along with temperament.

I am in my mid-thirties though and I can't recollect having run more than a mile before in my life. Maybe I will get used to this high and stop feeling the difference. Maybe I am feeling the kick because it is novel to me. But yes, it is nothing like the high you get from smoking marijuana :)