As long as the applications support Nas [network attached storage], there is no real reason to avoid Nas.
Exchange is one example of an application that does not support Nas, and most high-end database applications use San [storage area network]. Remember that Nas works at a higher layer and offers more intelligence but introduces a bit more latency that limits performance. San platforms also have the benefit of incumbency -- it's already deployed in the organisation and supported with experience and expertise.
I believe that Nas is great for the world of persistent data, and San is great for the blazing fast transactional world, so I like a combination of the two. But it's all based around best practices. I know companies that have an all Nas environment, though maybe they throw in a little iSCSI to support email. Those users employ Nas with high-end mission-critical databases and it's working fine. So there is no absolute method or approach -- it's all about what you want to do, but I like the idea of merging these technologies together so that multiple protocols can be served up for a single storage system.
Check out the entire Nas FAQ guide.