My answer is based on own experiences.
(our website exist now a few years and in our line of business we have good results if it is about pageranking, which also is made possible by using a (imho)good and even cheap sitemap generator)
Back to your questions;
Yes it is very important imho because the content is the most important part which you make public for all. It is -the- trigger for ppl to go/come back to your website.
The earlier google knows you have new content (with the most sitemap generators it happends automaticly) the earlier it will be shown (because the crawler will visit your site more often for new content) to the big public.
When ppl use google and type keywords/tags which your site (content on pages/postings) maybe also has, makes it possible that your page(website) is showing up on the first page and in best case even ontop (or near) of the first page google shows to the public, that would be great isn't it?!
(ofcourse is your content, the way it is written (good keywords are important) the most important part to get a good pagerank, but google has to know about it by receiving a sitemap)
All content could be/is important so also dynamic content, so why skip dynamic content if it is part of your website and (if interesting enough for the public) also is again a trigger to receive more viewers/readers/guests or customers.
As there are many sitemap generators there are also different ways how they (those tools) handle (new)content.
As mentioned above we use a sitemap generator but it is not googlesitemapgenerator but XML-sitemap generator we use. http://www.xml-sitemaps.com/
- There is a possibility to try the free online sitemap generator. (limited to max 500 pages if I am correct) http://www.xml-sitemaps.com/
- Or you try the free trial download version: http://www.xml-sitemaps.com/generator-trial.html
- And if it is some you like you could buy it for about 20 US$
1. Our sitemaps are created automaticly (cronjob) 2 times a day and the results forfill our (and our users) needs.
2. XML sitemap generator is not "messing" with apache.
3. We only create a sitemap for our content pages (2K+) not for the images(60K+) which are used with the content.
4. We don't allow google to also crawl our images (by using robots.txt and .htaccess)
5. Decide which is the best time/moment to create your sitemap(s), and don't overdo the amount of creating new.
Because everytime it is created, it (the sitemap generator) can send a signal to google that you have new content, even if it is creating your sitemap without new content.
There are rumors that, when the google crawler doesn't find any new (although it got many signals during a day from the sitemap generator ie. because it creates to often needless new sitemap(s)) google could punish you by setting your site back (lower) in pagerank.
A darn long answer but hopefully it helps you to find the right sitemap generator.