I've gone through periods of very high cannabis use, but recently i've massively reduced my intake. But i think its the frequency with which i smoke - everyday - that can be damaging in the way i described. It doesn't ruin my life: i won't lose my job, and i can still go about my normal duties perfectly fine. However my tendency is to do the minimal amount possible to get by, instead of excelling and doing anything above and beyond that.
100% agree with your assertion of heightened imagination and visualisation, it also changes your thought patterns in such a way that your train of thinking may lead to interesting perspectives that you would have never otherwise arrived at. It's what drew me to cannabis in the first place; intellectually i was intrigued by the creativity cannabis brought on. That said, a creative mind does not a productive person make! it's one thing to visualise etc. but it's the doing/execution part that seems so far out of reach when you're under the influence of cannabis. At least that's what i've come to realise.
As for habit-forming, I've always smoked cannabis with tobacco, but never smoked tobacco alone. This puts put me in quite a unique position in that after ten years i clearly have a nicotine addiction, meaning my use of nicotine is so entwined with my cannabis use that it's hard to mentally separate the two. Over time it occurred to me that i could never be sure whether i wanted to get stoned because i enjoyed the sensation, or whether it was purely for want of nicotine, with getting stoned being a proxy for that. Interestingly, i have recently quit smoking cannabis inasmuch that i now use a vaporiser to get high, which means i have also cut out tobacco completely. It's been around 5 weeks since i last smoked cannabis with tobacco, and i definitely have less of a want to get stoned, so i guess my suspicions were correct - nicotine was fueling my cannabis habit to some degree.
That link was intriguing, especially the inverse proportionality of benefits vs. dose size. It must be remembered however that the drug administered was a synthetic form of THC, not actual THC - presumably there were modifications to the molecular structure else they would have just used a THC extract straight from the plant. I'm sure it can still be taken as indicative of potential benefits of actual THC as a therapeutic drug though.
I think overall i'm just going through a transition period in my life, a slight epiphany; realising that i've been abusing cannabis and that my use has been detrimental to other areas of my life. My recreational use grew into habitual use, which brought with it a constant lack of boredom, leaving me unproductive and demotivated. I expect that i'll have all but given up cannabis within a year, if my current trend of usage continues. Maybe i'm just growing out of it, or that perhaps my desire to be productive is finally outweighing my desire to get high. Either way, i feel good about the changes.