If you're comparing Intel clock speeds vs. AMD clockspeeds, I can see where you might think that it's not as important to AMD.
What's actually going on there is that the pipeline structure for instructions is far different for each company. Intel went with a deeper instruction set (31 depp if I recall) and what happens is they can go higher in clockspeeds with it, but do less work per cycle because of the many steps each instrution has to follow to execute.
AMD, on the other hand went with a different way of thinking, and did a much more shloow pipeline (either 13 or 18, I think). This allowed them to do more work per clock cycle, but limited the clocking ability somewhat.
Trying to directly compare clock speeds of Intel to that of AMD is a true apples to oranges comparison. Enter the A64, and it gets a little fuzzier yet. I'd take a 1.8GHz or 2.0GHz A64 over an Athlon XP @ 2.4 to 2.6 any day. Again, AMD trys to get more work done per clock cycle, instead of just making the existing architecture go faster.
Now there are a lot smarter people on this site than I am, and I'm sure some terminology corrections will follow, but this is the gist of it.
Hope this sheds a little light.