I did FAWM a few years back, and while it basically consumed my entire life that month, I got an album's worth of new music out if it! Putting myself under a deadline really helps me stop procrastinating and actually create new music.
The last few years though I've been unable to do it. February is the busiest time of year for me gig-wise, and I can't see myself playing a 6-hour show, then coming home and spending four more hours writing.