Gives you a view of the other side of the fence. I get to see what other people put in as submissions. I get good ideas and exampls of what not to do.
When I was first learning design / layout I used to spend alot of time surfing the web for ideas and inspiration. Now that I run a small firm I make excuses about not having time and this forces me to do some just plain surfing. Most the areas I edit in have little commercial influence and are in my offtime interests.
Somewhere around 2 years, on a weekly basis anywhere from an hour to 15 or 20.
It's been cool, it's helped to get jobs (like Brownsmurf said, it looks good on a resume). You get to help build up categories of interest (skiing:) for example). Overall, a very worthwhile project to get involved with.
I run two sites in the category I edit, both already listed btw...partly I wanted to add a whole bunch of sites I knew about that hadn't been listed (improving my link pop as a nice side effect *grin*)...partly I just thought it needed doing
I once edited a tiny category in the back of DMOZ somewhere... From an SEO's point of view: 1. It teaches you what kind of titles and descriptions will and won't work 2. Helps you understand the submission from an editor's viewpoint, and the guidelines they (and you) have to follow 3. Keeps you in the loop as to which cats are understaffed (i.e. with lots of unreviewed piled up), and any problems that are occuring (change of policy etc.) 4. Far easier to talk directly to specific cat editors about issues 5. Instant submission if you edit the cat you're submitting to.
Because the category I edited was so tiny, I spent less than an hour a week on it, but the experience definitely helped understand how DMOZ and other directories work.