I have been working on CS5.5 for the last couple of weeks, and its been a nightmare. I like many, have been seeking a way forward from Final Cut.
I purchased the Quadro 4000 card, upgraded my RAM and installed an internal RAID. I love the idea of Premier but it seems to be a bad fit for Mac from all I have read. I have been working in an H264 timeline, and the stuttering makes it impossible to work with, unless I render. I have checked CPU performance and RAM performance, and this is not the issue. I have yet to try editing a sequence with Pro Res, maybe that will be much smoother?