If you have access to the DB and PHP then write a script to generate a sitemap for you I do this with my site and the site map generates in 5-10 seconds for 100000 urls, splits the xml files into 50000 chunks (limit for google) then creates a master sitemap file to link to the generated sitemap files
I haven't used google sitemap creator yet as it is still in Beta but the only other i would recommend is www.gsitecrawler.com . It works well even with dynamic urls, takes time to make sitemap depending on the size of the site but google loves sitemap created by gsitecrawler.
I think one should use their own xml sitemap generator. its a small php script, just upload and make unlimited sitemaps. can download it here : http://www.zeescripts.com/main/php-script/unlimited-xml-sitemap-generator-php-script-software.html
you can build you stiemap by the tool “Site Map Builder .NET†or the website:http://www.xml-sitemaps.com/
I go with Sitemap Writer Pro, because it's crawling is very fast and it creates sitemaps with 6 million URLs.