A general comment about signature links... My sense is that they count a bit but not for competitive terms.
Here's a bit of data which demonstrates why I say this... Recently (end of October), I noticed that my forming an s corp
site had dropped off of Google's first page for a couple of key terms, s corporation and s corp.
Some of the sites that jumped above them are what you'd expect. (Sites with tens or even hundreds of thousands of links.) But two sites really caught my attention. One site named s corporation dot com jumped above me. As far as I can tell, the site has (or had) a single link--though from a good trustworthy site: the Deloitte Touche alumni site. (Deloitte Touche is a big accounting firm, so a link from that site to a site about a particular sort of tax accounting classification seems pretty good.)
Another site was for a Washington DC area temporary staffing firm run by a woman named Sandy. She had named her site s corp dot com. I'm not sure whether the "S" stands for staffing or for sandy. But her site also crawled ahead of mine with a few dozen, er, modest quality links.
A couple of other points. Both of the sites mentioned above have been around for much longer than mine has. I think I've been around for maybe two years. They've been around for maybe 9-10 years.
Also, I have lots of junky, oh I mean, modest and low quality links. (Perhaps a couple thousand.) But I also have some pretty good links from business schools and from accounting and tax publishers.
Sorry to go on so long, but my take away is that yes of course links matter. But I was surprised to see an old site, s corporations dot com, with a single (albeit good) link jump above my site on the basis of (apparently) a good domain name. And I'm thinking the same thing is probably what's happeneing with the other old site, s corp dot com, which is also an old site with a handful of modest value links.