Our company has clients on 2 unix servers switching to SQL 2000 servers. It seems that many folks like the stability and reliability of unix, but the fact is that MS has made their products much more stable and the product integration, support and tools are far more plentiful and sophisticated than what is available for Unix. I'd hate to see Unix fall to legacy status, but I'm noticing a trend. Unix is still rock solid, but its being pinned into a niche as just a stable data server, and todays GUI, web app world require more capability from its data server.
Perhaps linux will be the saving grace for our beloved unix. Red Hat is doing some cool things. The problem, however, is that the linux community is plagued by non-standards. We need standards and compliance so all linux dist work in a common similiar fashion and that apps and toolsets work and integrate easily among all dist of linux.