I smoked everyday for years, now smoke only on weekend, sometimes not for weeks at a time and it's getting less and less frequent, don't feel much different health wise with reduced consumption.
I think I'd find it very easy to stop completely, never really crave it now and could stop tomorrow, I can't say the same about drink, being Scottish! Beer is definitely worse for you IMO and more addictive, I should mibby try giving that up instead.
I have lots of friends who smoke loads still and it doesn't seem to have lead to long term health problems for anyone I know, I think they were all a bit mental anyway, don't think the weed has altered them much. Saying that I can understand why people would want to stop, and more power to them if that's what they feel they want to do.