I think iSCSI is mature enough. It's been around for several years now, and I remember reading an article just a year or two ago where there were more than 1,500 iSCSI SANs deployed, mostly in SMB [small and medium-sized business] markets, but certainly it's developed enough momentum that it's here to stay for a while. Some of the indications are that major operating systems are building support for iSCSI right into the box. Both Microsoft and Linux have iSCSI initiators available right out of the operating system. Linux even has iSCSI targets in there.
Another indication that iSCSI is ready is because there is definitely a business need for cheaper connectivity, especially in large enterprises, for lower-end platforms like development systems or maybe distance-challenged systems -- systems that are not immediately in the data center and still have needs to get to the centralized storage on the SAN. Major storage manufacturers are supporting it natively. EMC, Cisco and NetApp all have iSCSI targets built into their major storage platforms. And then the major adapter manufacturers are selling and supporting it. For example Intel, Adaptec both have iSCSI HBAs [host bus adapters] that both have built-in TCP offload engines, TOE cards. I'd say the market has accepted iSCSI as something that is here to stay. And there is a business need customers are asking for, so yes, I think iSCSI is mature enough.
Listen to the iSCSI vs. Fibre Channel podcast here.