freejung - 4:48 pm on Aug 13, 2010 (gmt 0)
I've seen cases where one link makes a noticeable difference, and cases where it doesn't, so there's no guarantees. I've also seen it take a long time, up to a matter of months, for the full effect to be felt.
I bet you'll get benefit from this in time.
It is probably better if the rest of your backlink profile is reasonably good - that is, if this isn't the only real link you have. This is just speculation, but it makes sense that one really good link in an otherwise lousy link profile is not going to do you much good, as that would be regarded as an anomaly of some kind, but a really good link backed up by other reasonably good links will probably count for something.