If you enjoy IM (and who doesn't?) on the Mac and are not using Adium you are missing out. Adium is fast, has a friendly UI and is generally very stable.
As a frequent Skype user I find myself annoyed by the fact that it crashes incessantly and the lack of integration with my primary IM client.
Today I decided to install the Skype plugin and it somehow it made everything blow up. I could no longer start/stop Adium or Skype and had to throw both away, clear the Library and re-install.
My immediate thought (after "oh, crap") was what would have happened if I were running Windows and had installed a wonky MSN plugin? Odds are I would have had to go to some registry setting instead of just deleting the item. The average computer user has a better chance at performing an exorcist than they do of fixing Windows registry issues.
I am sure the author, who generously donated the plugin to the Adium community will fix the issue. You should throw him some PayPal for all his hard work.