dvduval - 5:22 pm on Aug 14, 2010 (gmt 0)
@Makavelli2007 - I try to read carefully what people like Matt Cutts say about directories, and based on that I would make sure you have reviewed these points carefully:
1. You should be adding quality content too, not only depending on user submissions.
2. You should be making sure titles and descriptions are not spammy, but reflective of the site.
3. Having a review process means that you don't let any link into your site, and this includes people who pay you.
4. It is okay to charge for the review process (for your time reviewing sites), but you need to be very clear what you are charging for.
Additionally, I would add that directories can have all kinds of additional features from video to articles that make them special. It is your job to make the directory special. If you do a good enough job, you will attract some natural inlinks as well.
With regard to building a niche directory, I think you are right on track, because it limits the scope, and increases the potential for quality.