In reply to ilona zonnenfeld's post on Mon 6 Aug 2012 :
In terms of the programs editors are working on--I'd say that in my experience, up until the introduction of FCPX, the vast majority were on FCP7. But now that Apple has stopped supporting FCP7, we are in a weird in-between stage where there are still a lot of projects cutting on FCP7, but there is a sense that as the OS continues to get updated, at some point you just won't be able to run FCP7 anymore. So I think a lot of people are transitioning to Avid or Adobe Premiere (in my experience, mostly Avid).
Also, I am not sure that 5400rpm will be fast enough--I've always done 7200.
Right now I am cutting an HD project (FCP7) on a 2010 15" MacBook Pro, and it is working fine (although I should note it is a short, and I'm able to do it using one FW800 drive). If I were you, since you have to finish on FCP7, I might look into getting (or borrowing) a used system, possibly a desktop. My top concerns would be connectivity and drive speed. Because desktops have more connectivity options, and they are just more powerful than laptops, I'd say that usually a desktop model is preferable for cutting features.
Hope this is somewhat helpful.