I mentioned trying linkwithin a few posts ago and I've neglected to write a follow-up post. Here goes:
LinkWithin gets a definite "thumbs up" from me. I've been following my stats, and LinkWithin has definitely breathed new life into my blogs. Sometimes it even causes me to go back and look at some of my old posts I've long since forgotten.
It has been great from a technical standpoint, too--the widget has worked flawlessly on all of my blogs. I'd recommend it for anyone who has been blogging long enough to build a collection of articles.