who says boards will be 150-250$? and the only real loss is the price paid on current boards if you bought AM3 thinking it would be BD compatible, which ranges from 50-200$, with most AM3 boards being about 100$, and were out for quite some time before BD comes out letting you use your DDR3 for a while.

the platform compatibility from AMD has been INCREDIBLE for the last half decade. and you may GET MORE PERFORMANCE out of the newer boards!!!! how you wonder, well with the new power features, it can probably drop idle power for cores not being used much better than we currently get, which means theres more remaining TDP left to overclock the cores being used. so with AM3+, low threaded applications may have a few extra hundred mhz due to better power management.