The short answer is that the products are absolutely ready. It's taken three or four years to bring the products to this current level of maturity, but I can say that key products from the major players are all ready.
For the sake of completeness, storage virtualization has also been applied to files and blocks (e.g., iSCSI). On the file side, there are the V-series products from Network Appliance Inc. (NetApp), as well as offerings from PolyServe Inc., Exonet or Isilon Systems Inc. -- those products are utilizing storage virtualization principles with a file focus in a homogeneous environment. On the iSCSI (block) side, it would be fair to include companies like Intransa Inc., LeftHand Networks Inc. and EqualLogic Inc.; each offering homogeneous virtualization products for their own storage boxes.
Check out the entire Storage Virtualization FAQ guide.