In particular, for those who use a DVX100--does a separate light meter seem worthwhile in gauging the proper lighting exposure for the camera? Or is a white/gray card enough, if even that?

This topic has been discussed quite extensively. Do a search and you'll find the varying thoughts on light meter usage. Most use the zebra pattern to judge exposure. Next step up, use a monitor and/or waveform monitor. Light meters are used by many professional lighting people, directors etc. to help determine lighting ratios, light placement etc.

Okay--thanks!