It was not the happiest time of my life, but not the worst either. I became pretty reclusive, and spent of lot of late, late nights walking around Minneapolis, sitting on the Stone Arch Bridge[1], watching insane late-night American TV / infomercials / televangelists, playing the guitar, and reading Hacker News. I maintained or even strengthened my interests in technology, but probably absorbed very little concrete knowledge at the time.
By less able to function, I mean I would've been utterly useless to an employer, or as a student, etc. I wouldn't have had the focus to complete any sort of complex project, software or otherwise. I did, however, manage to make some money ;)
So while I was not terribly productive, it did (I think) make me a more empathetic, positive, and less materialistic person and pushed me to make decisions that were ultimately very positive, like selling most of my stuff and moving to Cambodia! Still, I wouldn't recommend it and no doubt some of my behaviour could have incurred terrible legal consequences. My parents were definitely worried too.
[1] http://www.waynemoran.com/blog2/wp-content/uploads/2011/11/s...
What do you mean by permanent exposure? Regular? If so, do you have any sources to back up your claim?
The right perspective here is that LSD is well tolerated by the human body, but we do not know what its effects are like when taken over a long period of time.