How big of an impact does NUMA really have? I was reading up on Non-Uniform Memory Access (NUMA) and I was wondering how much of a difference it can really make?  Another way to word that, what level of throughput is required before this becomes beneficial?

Also, what type of server do you need to look for when you want a system with multiple system busses?
Jonathan Kehayias did a good blog post on NUMA at SQLSkills.com. 

I believe server wise most of the vendors out there note if they are NUMA capable servers or not. From reading Jonathan's post it seems the focus is on the motherboard and processor capabilities. Then I would imagine how they interconnect would be an important thing to note as well, since that would be the bottleneck in most cases.

I have not really seen anyone write up on when NUMA becomes beneficial. I think it would just be a analysis on what your system is going to need. If one server maxed out to the nines is not going to cut it for the workload, then look at the alternatives.