SincerelySandy - 12:49 pm on Mar 31, 2007 (gmt 0)

Here's a couple thoughts, not facts, just thoughts...
As new links age, they are being percieved as having more value and higher quality by google. So to see the real benefit of a link, the link needs to exist for more than just a couple months.
Often it doesn't take much to go from page 3 or 4 in the SERP's for a keyword phrase to page 1. But if you are already in the 6th position on page 1, it can be real tough to just to move up a couple more spots.
I would not stop building quality links just because google isn't showing you any love for it yet.