Hi Kim,
meta-data specifically for CCA is a re-usable item. It [i]can [/i] be used to show a route for a call.
For example; attaching some form of customer data to an interaction at a pre-defined entry point (RP or similar), then reporting it as a KVP/Filter, via DMA at that point and subsequent points throughout the lifecycle of the interaction can be used in a calculation at those points along the way and also at the delivery/target, to show the volume of calls which took that particular route, down to an Agent. Something like:
meta-data/KVP to show [b]Customer Value=XXX[/b]
[b]KEY: [/b] [color=red]Object:[/color] [color=blue]Volume[/color] (narrative):
[color=red]RP 1:[/color] [color=blue]250 [/color] (Exited the Self Serve/IVR)
[color=red]RP 2: [/color] [color=blue]125[/color] (Waited in the Queue)
[color=red]RP 3: [/color] [color=blue]25 [/color] (Overflowed to another Queue)
[color=red]AG 1: [/color] [color=blue]10 [/color] (Delivered to an Agent Group)
[color=red]AG: [/color] [color=blue]3 [/color] (Delivered to a particular Agent)
- There are obviously more uses - this is just an example, to get you thinking

I really can't think of an example of when you would [b]not [/b] want to use meta-data, unless you are attaching it from an unreliable source(?) That is, if you are using external information for routing or reporting purposes, make sure the source data is up to date, relevant and does what it says on the tin, otherwise both routing and reporting can suffer.
I hope this helps?
Tony