What I like about Twitter as you do connect with people you might have not heard about before- other artists, small boutiques, unusual companies for instance.
Also I have found the names of some people in publishing, retail and the big magazines which may be of help further down the line.
Also it is nice to meet people from all over the world.
And a nice tweet complimenting your work can make your day.
I do think most people on twitter are businesses so therefore more there for self promotion. So I think if you look at as more of connecting/ networking tool than "instant sales" you will enjoy it.
I have been contacted by several people on there wanting to licence my work, join their market place, interview me etc and so on so a few opportunites have come about on there.
By the way you can add images of your work on there.