The simple NBench benchmark shows that you can compare the memory/integer performance of the N900's OMAP3430 to a Desktop PC PIII or K7 with the same or even higher clock frequency: http://www.tux.org/~mayer/linux/results2.html.

FP performance is a different point but I'm not shure if the compiler/benchmark really used VFP/hardfloat. Also gcc version seem to have a great influence as later versions give optimized and better results.