So you are using it to post updates to the people who already are interested in your game? Like a focusing point, not a way to get new players/traffic?
Both, I guess. It definitely serves as updates to the people already interested in the game, but it also brings in new people now and then. I haven't really done any marketing as the game is still a couple of years from being finished, but the updates (and videos in particular -- I'm sure RPS wouldn't have written about it if there wasn't a video) have generated some attention. I think just the fact that potential customers can see that it's a game that's been in development for a while and that I'm always working on it means that they're more likely to get invested. And when they're invested, they're more likely to talk about it elsewhere and bring in other people.
Right now I'm using various gaming forums for this. Any comment on this? Should I switch to a blog and just drop a link to my blog on the dedicated gaming forums?
Just dropping a link to your blog can be perceived as spamming. I have a DevLog here and a thread on the Ubuntu forums where I copy-paste some blog posts. I don't post all updates on those forums, though, just the biggest updates (new gameplay mechanics or releases, for example).
Also, haven't you thought of using your own forum for this instead of a blog?
A forum requires a bit more involvement from people, and forum posts with updates aren't as immediately apparent as they are on a blog. I follow the Wolfire blog and the development of Overgrowth, for example, but I'm not a member of their forum and have never really read it.
What I have done, however, is connect my blog with my forum, so that the blog post automatically gets posted on the forum, and instead of separate blog comments, the blog post links to the thread comments. I did that to avoid having two parallel 'communities' -- one in the blog comments and one on the forums. The downside might be that casual visitors are less likely to post comments when they're made on the forum (even though I allow guest posts on the forum, so they don't have to register).