Sure, we can get a MacBook Air with 64GB solid state disk (SSD), but what about upgrading a MacBook Pro? Ryan Block put one in his MBP and got a 20 second startup. Ridata released a 128GB 2.5“ SATA SSD in January that looks compatible with my MacBook Pro. Newegg has it for under $500. For comparison, however, a 250GB 2.5” spinning platter SATA drive can be had for under $100.
Corrected: I had originally written “128MB” above. Jon Link pointed out my error.