Yep, I think we crossed that line with the release of Intel's Core2Duo line of processors. My 2010 MBA actually uses the C2D 2.13ghz, 4GB ram, and a 256GB SSD and it performs perfectly fine for 99% of my uses. Only time I feel bogged down is when I run multiple Play! Framework modules at once.
I remember when the first C2D benchmarks were released, it was hilarious at just how much faster they were than anything else around. Poor AMD hasn't recovered since...