A year or so ago, I was an online member. In terms of jobs postings it was so so. A little more than what you would get from say Taxi (of which I was also a member). These were soundtrack composing film jobs to apply for. Also, it seem there would be jobs in addition to composing, like composers assistants, music supervision, and liscensing jobs. So I think it's like a lot of self employed artist situations: It's not foolproof, but it's a tool in your toolbox, along with networking, cold calling. I think some people on this forum have laughed at 'Taxi.' But I think it's what kind of music your doing. Taxi, I think, is for pop/contemporary mainstream music.
While in NY I did enjoy going to some of the forums the FMN sponsored. BUT I did not enjoy paying a fee to show up. Evidently the online price was not the full FMN sign up price and there was a difference to be paid. SO, I would only go to the real live forums with REAL composers working, not some history crap they would sponser. So I wouldn't go every month, maybe 3 or 4 events a year.
Some of the other resources at the website were cool. You get salary surveys and such. When I joined it was $10 a month, SO not too bad. You get more out of it than just tip sheets.