I have a 2006 Ford Escape. I was incredibly close to getting the hybrid version. Remember that when you're doing freeway driving though, the spread on mileage isn't that great. The efficiency of a standard gas engine goes up and the efficiency of the hybrid goes down because you don't get as much assist from the electric motor. Once on a storm though where there is a lot of starting and stopping, and slower driving, you probably wouldn't use the gas engine much at all as everything will be fully charged from the previous driving. It also would make for a quieter video time near your car. You won't need to get as far away to avoid the engine and fan sound pollution.
That said, on the longer chases I averaged about 21-24 MPG with the 3.0 liter engine depending on number of passengers and how the chase went (long straight drive vs. lots of stopping). I imagine I'd be up around the 25-30 MPG with the hybrid, with the chases where I'm stopping a lot or end up being close to my target so I'm just moving along with the storm and stopping and taking lots of pix and video being over 30 MPG.
If I trade in again in a year or two (which I do plan on doing) I'll again very much consider the hybrid. Not only for gas price sake but just also for some peace of mind. I have to remember that this vehicle also sits in rush hour 5 days a week... I only wish I could chase that much.
-John