The grass always appears greener. I buy a new MBP at each processor change and have yet to be blown away by a huge performance increase. It will be an improvement, but nothing like it appears.
For me, any CPU, GPU or memory performance increase is almost always brought crashing back to earth by having to still use hard drives and slow networks so they're largely irrelevant unless you're a gamer or do 3D CAD or something CPU intensive. So like Aatos, a new CPU boost is nice for about 2 weeks and then it's meh again as soon as your hard disk is thrashing away or you've got to ftp a few gb and it's no faster.
I wish someone spent the same amount of money and energy on solving fast, cheap storage and networking as Intel spends on pointless for 90% of the populace CPU upgrades. SSDs are getting there slowly but still expensive and limited in capacity. Networking has been stuck at Gigabit for ages and then runs smack into broadband speeds. It just seems like we're solving the wrong problems here.