its use full if you are having low competition; if there is much competition then you can't get good rank from directory submission alone
you should see them as 3 separated categories; 1) paid directories; I don't like those; most of them are just way to expensive for the value you actually get from it 2) free general directories, although most are indeed rather worthless, there are thousands and thousands of them, so the small % of them being worth submitting to are still about 1.000 directories 3) niche directories; those are many times the very best ones ... for your niche so, 1) only if you actually have huge budget 2) order at least 500 directory submissions from a service, but from a good one, so they use a good list, not an automated program 3) that you should do yourself and then I suggest; www.directorycritic.com and http://info.vilesilencer.com to look for them
Now a days directory submission were become useless. Instead of that I suggest you to do social bookmarking in selective website like digg, mixx, reddit, yahoo buzz and delicious. These are more effective way to get indexed in Google quickly. If you are a blogger and updating your blog frequently then digg & mixx is your best choice. Through that you may receive huge number of unique visitors compare with Search Engines. You will get decent number of comments for your post, if your content is interesting to read and useful to the target audience. Cheers!
Dynamic content on directories can and does help pages get crawled more frequently. Such items as random quotes, news, etc. can change daily. This would cause the search engines to index more frequently, but may not be a sign of quality. Regardless, the directories you listed in your original post are certainly of a high quality. The quality of a directory is best judged by the quality of its listings and the features the directory offers. If a directory tackles these issues, some will use it instead of a search engine to find what they are looking for. Submitters, on the other hand, have different quality standards. Google does a good job with displaying quality search results. Instead of searching for cache dates/times at each directory, simply search Google for what you are looking for. Google itself has determined what is "quality" and what is not and ranks them accordingly. So if I want to submit to a web directory, I search for web directory. If I want to buy energy efficient lightbulbs, which I need by the way, I search for energy efficient lightbulbs.