So is it only data transfer that is affected by the cap?
yup pretty much. someone else mentioned it already, but things like copying large files or having to read large files is where you'll see the difference. like i mentioned in my post, this cap shouldn't keep people from buying the new 13 or 15" mbp as you still get the major benefits of ssd. i've read this entire thread and it seems that the majority of people wouldn't notice this cap in day to day use had it not been discovered.