I recently tried using the directory plugin for a project but found that it was far too restricted in the customising area. Rather than just mumble a few mild expletives and move on to something else I thought it might be a bit more productive to discuss why I felt it wasn't suitable for the project I had in mind.
1. CSS inheritance. The plugin uses the CSS from the active theme - which is totally a sensible thing to do in order to have it integrate nicely into a site - but there is no 'custom stylesheet' option. This caused me a problem because the category titles are set as H2 which is way too big in the theme I currently use.
Suggestion: Offer the ability to apply a custom stylesheet OR have a settings page where you can set the size, colour etc of things such as catergory headings, listing heading, listing text etc.
2. Listing layout. My project is a business directory and I installed Custompress to handle additional fields. The additional fields are links to social networks, so it would be nice to be able to customise how and where those additional fields are displayed.
Suggestion: Have shortcodes for all of the listing fields and the ability to use them in a 'single listing' page that then becomes the template for all listings.
I don't mind digging around under the hood of a plugin but in this case it would probably take too much effort to make it just how I want it. I think my suggestions would be welcomed by quite a lot of people and would place this plugin ahead of other commercial products. Don't get me wrong - I do think this is the best directory plugin available but there are a couple of theme based products that are a bit more versatile right now.