@Twan - Wow. That is certainly a loaded question. I know that the Exchange team asked why we couldn't have Windows Failover Clustering and WNLB on the same servers so we could utilize WNLB on the multi-role servers, and the response was blank looks and "why would anyone want to do that?" Not sure if anything will ever happen there, but I don't expect it.
I'm not really sure why the Windows team chooses not to update WNLB. I haven't had any discussions with them about this in about 5 or 7 years, and was told at that time that we didn't think that the investment necessary to compete with the hardware load-balancer vendors weighed against the amount of revenue in Windwos this would drive didn't make a good business case. The big deal is that the biggest hardware load-balancer vendors have special chips in their devices where they accelerate the performance of what they are doing, and in Windows, we don't have that capability. I don't think we could really ever compete with the "big guys" like F5 or Cisco. Because of this, I would think we aren't going to see much investment in WNLB.
Of course, I want to make sure everyone knows that this is just MY OPINION - not an official Microsoft statement!! ;*)
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rgillies at microsoft dot com