Rose: The purpose of Seamonkey is to be more than a browser - it is a browser, an email client, a news reader, an irc client and a wysiwyg-html-editor in one single application. So if you look for a browser, use firefox. If you look for an email app, use thunderbird. Only if you want to have everything integrated consider using Seamonkey (not ;)).

By the way: on the project page they say that Seamonkey has tabbed browsing...

(fixed typo)