I made just this point in another thread. Even huge increases in CPU power and speed are not even noticeable "the vast majority of the time." The now humble Core-2-Duo chip still does everything and more that most of us need to carry out our day to day work on a computer. If you need a computer now and the MBP appeals to you, buy it, for heaven's sake! You won't regret it.If it comes down to looking at a chart, it might not matter that much.
Put another way, I just went from a 1.6GHz Pentium M to this shiny new 2.53GHz MBP. The new machine is easily three or four times faster than the old one, and the vast majority of the time, it's totally irrelevant. This is true more often than we tend to admit in this industry, which is why it's key to understand why, exactly, you need the level of performance you're paying/waiting for.