With Socket AM2 the (OEM) customer now has the option of DDR2 memory from AMD too. In theory, that should produce a higher memory bandwidth, which in practice is only achieved by the expensive top processors. Compared to 'old' DDR memory-based platforms, the bulk of AMD's CPUs cannot benefit from the higher bandwidth of the DDR2 memory. A closer analysis of the benchmarks even reveals a marginal performance deficit when pitting the 'new' against the 'old'. It's clear that DDR2 memory only begins to pay off at higher clock speeds of 2.4 GHz and above. And that in turn affects only the CPUs from the Athlon 64 X2 4800+ that have a price of at least $600.
My advice on the AM2 platform, is that if you can afford to wait for the next gen and/or for the prices to drop, you will be much happier.