To be honest, I don't like the idea of this merge.. I know Skype is owned by Microsoft, but they should at least keep the services separate. Not all people who use WLM use Skype and there are some who use both, so it wouldn't seem logical to those who use both.
Also, I use older builds on both Skype and WLM. I have to use an older version of WLM because it's the latest build for XP computers and I downgraded my Skype to a low number (4.1) because of the factor that Skype 6 slows down my computer more and Skype 4.1 lacks the advertisements.