So gothamm, what ur saying is dont buy a mac unless you have a nice fat trust find that allows you to spend over £2k a year on a smacking new top end MBP.
Cause even though the hardware specs are STILL better than those of the competitors a year later, your OSX is doomed because of Apples cartel?
Just drop firefox into the trash and download a nice fresh updated version from the mozilla website. Worked for me, I had firefox lagging bigtime.