I really didn't have any use for the features of Blur, and I found it to be an impediment. I very quickly went to LauncherPro, and I was delighted at the improvement in the UI experience. Furthermore, since I don't use "social networking" apps(I use my Atrix mostly for business), using just the free version of LauncherPro was all I really needed.
In my case, adding LauncherPro made my Atrix noticeably faster and more responsive.