Is anyone out there using a NAS or iSCSI storage solution as a low-cost alternative to a SAN? I have heard that some small to medium sized businesses are using these solutions in place of a SAN for things like SQL databases and email storage even though it has been discouraged.

Can anyone tell me if they have any experience in the SAN or NAS or iSCSI department and what you feel are the pros and cons of one solution over another??