If you have a suitable Mac NVidia card, you really ought to have a good go at CS5.5. The Mercury engine make things happen that are impossible with FCP. Premiere will play multiple streams in real time whilest FCP won't even play a single graphic overlay without rendering. Multiply this by hundreds of times when editing and the time savings are extraordinary. I use both FCP and CS5 on my Mac Pro, but if I want speed and integration with PS and AE, Adobe is unbeatable.
I just got the new higher end 15" Macbook Pro with the SSD. I think it should run well. I will probably get Final Cut X no matter what, since I seem to mostly get folks asking me to cut on it. I am concerned about how well Color has been integrated into Final Cut X, or I at least hope that it will still be a standalone application. I wasn't fond of Soundtrack Pro crashing so much, but I do need a solid way to do post on sound, with a good space designer/reverb and compressors. I am thinking that it might be time to get Logic whenever Logic X comes out in any case.