Don't worry about clock speed when comparing editing workstations. GHz is kind of like RPM in an engine - it's related to speed, but different cars can provide very different performance at the same RPM.
AJA demonstrated uncompressed 10-bit SDI editing on a 17" PowerBook at MacWorld a few months ago (with external RAID 0 FireWire). A complete finishing enviornment in under 10 lbs.
There is equivalent stuff coming out in Windows laptops over the next few months, but nothing yet.
My Book:
http://www.benwaggoner.com/books.htm
Cleaner e-book:
http://www.cmpbooks.com/cleaner/
Compression Class at Stanford:
http://www.digitalmediaacademy.org/compression.html
