I was planning to buy a Ford Escape Hybrid and I was still debating if its worth to shell out extra 5000 dollars for getting the Hybrid option..
I dont remember the article where I read that when the Gas prices touch 9 dollar/Gallon then its worth buying a Hybrid.

Currently, there is no financial justification for buying a hybrid vehicle based on fuel costs alone. In california, the tax credit and ability to drive in the HOV lane mitigate this somewhat, but unfortunately the Escape Hybrid is only eligible for the federal $2K tax deduction but not the california clean air tax credit. Click on the link below for an analysis from the WSJ's detroit bureau chief on his analysis of the cost benefits of owning a hybrid vehicle.

Also included is an in-depth analysis from Omninerd that breaks it down for you. Essentially, you should do it for the feel good environmental reasons and not necessarily savings from fuel.