As for Apple, they have gone too consumer and it's hurting their Pro Market. I certainly hope they don't discontinue the towers, otherwise, what am I going to use? I need all the power I can get from a computer and can't do my stuff on a laptop or an iMac.
Creative Cow has a workflow article about processing with Premiere Pro CS 5.5 on an HP Windows box.
He is a lifetime Mac guy, but moving to the Adobe metadata workflow with no transcoding.
I am a photographer who has done digital imaging since 1991 on all kinds of boxes - Dec Alpha workstations, Sun, IBM mainframe, Oracle databases, etc. Lots of different types of boxes out there that use the same i7 Intel hardware, but are 33% of the cost of a Mac, spec for spec. You'll do fine!