A: There are better ways to improve SEO results.
Google still uses PageRank, albeit in a much more advanced form than when it was introduced. For instance, trust is a component now.
If you are referring to the recent "Penguin" algorithm update, that targets web sites that are falling short of the Google guidelines.
Acquiring links from directories is a low-value activity. It won't gain much for you. Your time is better spent building viral content, like infographics, personality tests, quizzes, top 10 lists, scavenger hunts, etc.
Still, I should answer your question about judging a directory's quality. A good measure for a directory's quality in the eyes of Google is: Does the directory primarily exist for users or for webmasters. If the latter, move on. Google doesn't like directories whose primary purpose to entice webmasters to submit their links.