Since there was some interest on this topic and I'm still working with this gear in the lab I thought I'd dive a little deeper into what I've been finding and hopefully what you all might be interested in.
There definitely seems to be some value in measuring how these appliances affect network traffic and network application performance. However, there are several different ways to measure this. In my case, I'm monitoring the traffic from the ingress interface of the WAN accelerator and comparing it with the ingress interface of the adjacent WAN device. By monitoring it in this way, I'm able to clearly articulate the "before and after" effects on the traffic. Also, in some cases where I have two sites that are very similar in traffic amounts and patters, I'm able to compare the traffic of a device where we've deployed a WAN accelerator and sites that we haven't.
How would you optimally like to measure/monitor this traffic?