I drive a Ford Fusion hybrid, which I am extremely happy with. It’s a terrific car. It’s true that it some circumstances, e.g. highway driving, its mileage is not tremendously better than the sedan version of the car, generally high 30s versus low 30s. Although often, depending on the flatness of the highway, wind, whether I’m not driving at 70 or above, etc., it’s low 40s, higher than the EPA estimate, and much better than the conventional sedan.
Where the Fusion really shines is in stop and go traffic, or slow city cruising. The EPA estimate is 41 mpg, I think, but I can regularly get well into the 50s or more.
On the other hand, things like hills, high winds, and really cold weather take much of that away. But then, that happens to conventional engine cars as well. In general, the hybrid Fusion gets an average of around 10 mpg better in comparable conditions to the conventional Fusion. Lower than that in standard freeway driving, but much higher than that in slow city cruising.
When I purchased the Fusion, there were tax incentives and a short-lived state policy that eliminated sales tax for hybrids. I essentially got the car for about the same price as a comparably equipped conventional Fusion.
As much as I love it, I have to admit that the increased price premium is a bit hard to justify without the tax incentives. But I see that hybrid prices are coming down all the time. My best advice to people is to realize that the Prius is hardly the only hybrid out there, and by no means necessarily the “best,” which depends on the needs and desires of the owner. For me, the Prius was too uncomfortable, gutless, and noisy on the freeway, especially compared to the Ford Fusion. I decided I was ok sacrificing some mileage for comfort and more power, not to mention better looks. The point is, shop around! I think about every manufacturer these days has hybrid models, and many are very good. If it’s a less popular model, you might be able to get a better deal.
One of the biggest reasons to purchase hybrid, in my opinion, is how clean they are. Modern cars are of course very green these days in general in terms of their exhaust, compared to the past, but hybrids are even better for that than conventional cars by a lot. The ICE simply shuts off when you’re sitting a stop light, or are coasting at below freeway speeds downhill, etc. For me, the cleaner emissions was as much an incentive as the improved mileage.
The last thing I’ll mention is that the source of a lot of people’s poor mileage performance is shitty driving. E.g., accelerating faster than necessary, braking late and hard, not using the cruise control or not maintaining steady speeds, aggressive driving, not pulling through a parking spot so you don’t have to shift in reverse to exit, braking harder than necessary for a corner, etc. Shitty driving leads to reduced mileage on everything. I’ve known some people who bitched that their Prius wasn’t getting the mileage they expected, but then discovered they were trying to drive it like idiots. By which I mean most people. Of course I assume that SDMB drivers are better than average! 
One of the unexpected things I like about the hybrid, is that beyond the obvious it taught me lots of little tricks to get improved mileage, simply by monitoring the instant mpg readout and power delivery: tricks that don’t reduce the trip time, but over time make a huge difference in mileage.
My fob stays in my pocket.
