The best benifit is that forum signature link pass good value of backlinks and it is the best easy method to gain one way links.
On Dp its good for traffic -- if related. Its also good to build backlinks to your site with targeted anchor text. Anchor text is important because so many blogs are just linked to around the web from either your name (commenting) or the sites name. Unless your sites name is the major keyword you are going for, you will need to find valuable opportunities to provide quality anchor text linking to your site. DP is a good way to do this if you are sincerely posting and not just trying to build links.
make strong backlinks. If you have a thread on frond page it will give good result.. but don't spam on forums.. If you have domain with wordpress without any article. you may get PR with using signature with high post count and high thread count.
forums helps a lot to learn about the concern topics. It give all the info about seo and related things at web. and same time signature helps to give backlinks to site and brings some terrific to site..
From my understanding it does provide a small weighted backlink, but you really need to make sure that the anchor text for your link is related to the keyword you're trying to boost. Also works well if you have added new pages to your site and want to get them indexed by Google quickly.