I did the 60-day challenge last year... it was writing 30 hubs in 30 days and then spending the next 30 on some group marketing techniques. Writing 30 in 30 was really stressful to me because with my husband, three kids, and full time job, I don't have a lot of time to devote to writing. However, a few of the others doing the challenge with me really went out of their way to encourage and support me. That kept me plugging away and motivated. My family was very supportive as well, even though I'm sure I drove my husband crazy! I also found that the more I wrote, the more I thought of things to write about. However, on the down side, after the challenge I had some serious burnout and writer's block for a few months.
Yes, it did boost my hubscore. It still goes up and down at a whim, but for the most part it has stayed between 92-98 ever since. (I did make it up to 100 once, for a short period of time.)
It was a real confidence booster for me. I also learned so much in those 60 days! I plan to do another one at some point, I just haven't had the time to commit yet.