Cannabis has helped me with my sleep (chronic insomniac). This is the most important thing. It also makes taking breaks especially difficult.
It also makes anything that I'm working on a little more interesting and fun. I know that it does not sap from me my motivation to work, since my grades and hours spent working for the past 9 months has not faltered. My grades have improved, actually (senior-level electronics courses)
I also have suffered from an eating disorder. I don't seem to ever find myself going into that particular downward spiral of thinking, even when taking breaks from cannabis.
For some reason, it seems that cannabis helps me with my ADD. I'm not as impulsive and can be notably more productive, but this therapeutic window is generally confined to smaller doses. The anxiety and depression that typically arise simply don't. For 8 months, I was not able to afford my medication, and took a small dose of cannabis instead. I think the traditional treatment is likely better, but cannabis seems far gentler on my body than amphetamines (this is a subjective observation).
I'm one of the lucky ones. Despite being a nearly-daily consumer of cannabis, I can still have dreams (I just have a harder time remembering them). Sometimes if I have a lot (sativa-dominant), I have especially vivid dreams.
The biggest downside is that it dings my working memory a little (doesn't really matter since I take a lot of notes whenever I'm doing anything). Also, when taking larger amounts, I'm more likely to commit errors in speech (spoonerisms).
Overall, cannabis allows me to relax, think through things a different way, put things in perspective and take on the world at a slightly slower pace (which is a Godsend to someone who has a restless, impulsive, distractable mind).