I hate that feeling. I once had some weed so potent that I literally forgot how to put on socks. Sat there staring at them for what felt like several minutes, trying to remember how socks work. It's hard to imagine any scenario where that's a life-enhancing benefit.
Now into the third month of my experiment, I have smoked pot just twice. Both times it was after a gig, when it was 3:00 AM and I was too wound up and caffeinated to sleep. The caffeine isn't good for me, either, but my normal bedtime is 10:00 PM so without it I'd never make it through a gig.
Surprisingly, my sleep patterns have stabilized. I now have no trouble falling and staying asleep. I still sometimes get up too early, but "too early" is now 4:00 AM, not midnight. I can live with that.
Other benefits include a clearer head, reduced appetite, improved memory and increased physical energy. I also watch less TV and am less likely to procrastinate about doing unpleasant chores.
Manual dexterity seems to be improving. I am faster and more precise on both musical and computer keyboards, although I can't be sure how much of that is just due to playing in a band again. I will never again be the speed-demon I was in my 30's, but at 65 there's just no need to prove anything to anyone.