iSCSI - read about it on wikipedia but...

Do you mean the benefit of the expansion support, or iSCSI in general?

Thx Grievous for your prompt response...
Suppose I'm interested in iSCSI with respect to purchasing a NAS box that supports it...
How does iSCSI make my life easier? Would would I want a NAS box that supports iSCSI ?

It really depends what you want to do with it. The basic idea behind iSCSI is that you have a big file sitting on a network server(the ReadyNAS in this case) and you have a piece of software(Windows comes with an iSCSI client built in, just type iscsi in the run option from the start menu). When your client connects to that big file(could be 10GB, could be 10TB) your operating system treats it like a local hard drive.

The difference between treating your data on the network like a local hard drive, compared to what you currently do with your NAS is that the operating system of your client has complete control over it. You format it however you want, partition it just like a hard drive, you can install applications to it(and generally the application won't realize that it's not actually a local hard drive). The one thing that iSCSI doesn't do very well is multiple clients connecting to that same iSCSI LUN(iSCSI shares are called a target, then the individual files within each target that your OS sees like a local disk are a LUN).

Sweet - I think I got it! thank you :)