I don't want to knock your efforts, but rankings on google seem to be all over the place these days. Webmasters are saying how they are ranked well, and then are downgraded or sometimes disappear altogether.
Something to do with google wanting webmasters to use Adwords? Some may say that, I couldn't possibly comment.
It is often mentioned that to rank well on Yahoo and MSN, it is better to have as many backlinks as possible, even if they have very little
PR, unlike google. This seems to apply especially to MSN.
More backlinks the better.