Yer true. Mhz doesn't mean crap (as seen on many a post on Amiga.org). .
One can't rely on just IPC i.e. as AMD has stated "Instructions per cycle"(IPC) x "clock speed".
Note that Intel plans to increase thier own IPC increases via Prescott and Pentium M cores.
Even the x86 world has drastic differences now. AMD Athlon XP 3000+ with the barton core running at 2166Mhz (or thereabout) compares very well against a P4 3.06Ghz in benchmarks and real world tests...
Dependent on the applications being run. Relying on IPC alone has limits.
Note that AMD Athlon64/Opteron 12(integer)/17(floating point) stage pipelines for clockspeed increases. AMD did recognized that they need clock speed increases in the near future.
Athlon XP only has 10(integer)/17(floating point) stage pipelines. The current AThlon XP 2800/3000+ could be overclocked @ ~2.4Ghz without going to liquid cooling (i.e. head room reserve for future and last K7 Athlon XP 3200+).