I have used Evernote for quite a while, I ran into this blog post from a re-tweet on twitter.
It is a post from the EverNote team about re-writing their application in C++ from WPF
http://blog.evernote.com/2010/10/26/evernote-4-for-windows-is-here/
I find this interesting that a development team is moving away from WFP. I am not surprised that there are WPF performance issues, however I don’t this this is a knock on .NET.