This could be true (I really don't know), but it is a fact that the success of overclocking doesn't only depend on the CPU, but on quite some other factors as well.
If you buy a P4 based on the Northwood core, you could get some nice overclocking results. Don't push Vcore over 1,70 though, since this has killed quite some P4 CPUs
As I see you overclocked your CPU 540Mhz. This is a nice 30% overclock and I wouldn't consider that to be a bad result. I'd rather save my money now, and buy a P4 with 533Mhz FSB and a P4 board with 800Mhz FSB in order to get some nice OCing results. I haven't read that this has been done yet, but I am quite sure this will be done in a couple months (as the yields of the P4-533 are quite good, this shouln't be that big a problem I guess).