It depends on how you feel. Some ppl don't mind MJ but personally, I do and such a smell would cause me to cancel the trip. That said, you shouldn't have to cancel a trip for such reasons, and Uber is supposed to take such comments/accusations seriously (well, they used to).
If it were me, I would note it in the comment section or send a separate email referencing your trip. Tier 1 should pass it on to the higher ups BUT this is no longer guaranteed as they are in Manila and there is a serious language barrier with some of these agents ( many of them just aren't trained very well).
For drivers though, anything less than 4 stars is just as bad as a 1 BUT , if you felt you got to your destination safely, just give 3 or 4.
This is just my thinking but if a passenger caused that smell to linger in his car, the driver should have went offline to air things out or at least give you a warning when you got in, as a courtesy. They are NOT obligated to do this, though, and the driver might not have been aware of the need to since Uber is very cautious in telling them how to do their jobs (as contractors).
If it is his first "offense" he'll prob get a warning but he'll be ok.
PS: Your phone number is masked within the Uber system so the driver doesn't have your number unless you gave it to him.