I find the FSB isn't all that good an indicator as far as overall performance goes. AMD chips with an FSB of 266 performed much faster than Intel chips with an FSB of 600 or so. Yes, an FSB of 667 compared to 167 is pretty significant, but the use of an Intel chipset may all but eliminate any benefit that that brings.
Can you explain what you mean? Usually, when people say bottleneck, they mean that one component of the pathway is much slower, or allows through less data, than the rest of the pathway. And so that component sets the pace of the whole system. In this case, the FSB speed is closer to the processor speed, so there's less chance of it being a bottleneck. Then again, if I understand correctly, minimizing this effect is the whole reason you have a cache on the other side of the bus....