During the wireless audits I have done, once I was on the network I did an assessment of all systems on the network (as was the level of permission for that particular audit). The point was to show what could be seen and the vulnerabilities associated with them. We wanted to avoid people saying that getting onto the network was no big deal. Logging into routers and vulnerability testing development servers really opened their eyes.
We also noted any systems with WEP encryption and did not try to break the encryption (mainly because of time and the scope of the audit). By the time of the audit it was pretty well known that WEP could be broken over time. We then just asked for the network diagram associated to the AP in question. We then pointed to the other evidence we had obtained from the unencrypted network and let them make the correlation (which, thankfully, they did).
Had this been an all out penetration test, well, we would have had even more fun.

Hope that helps,
Cutaway