Since your questions are about the '08 FEH 4WD, and I actually have one and live in Denver, let me tell you what I know.

Snow: I've had it since March 3 and driven in snow several times with no problem. In February before buying, I borrowed on and tested traction in icy areas. I found traction superior to my previous Subaru from a stop. It's not as car-like as a Subaru on the road but still nimble. My neighbors have had an '07 FEH since late '06 and driven 2 winters including lots of mountain driving. He and his wife both said it's the best vehicle they've owned for Colorado, but keep in mind they're transplants and (like many new residents) thought they needed truck-based SUVs like XTerra and Explorer which generally are not so great in Colorado. So they might not know what a real AWD car (Audi, Subaru) is like. As for crash test info, I did not look at that and can't comment.

Storage: You should start it (and drive if possible) for 5 minutes every 2-3 weeks. I have found that lots of these battery tales are started by people who have not actually owned a hybrid and who extrapolate from experiences with unmanaged devices like a cell phone or a flashlight. Just follow the manufacturer's recommendations and you'll probably be fine.

Stability Control: Ya it stinks that they didn't include it. Ditto the steering wheel audo/climate controls. It's just cheap and stupid not to have it at these prices and it's something I simply had to deal with. But at least the ABS is very good and the vehicle tracks well. I would recommend a test drive up Golden Gate Canyon if you're not sure about hill climbing/cornering.

Seat Heat: I don't like them because they get super hot. But I'm fairly fit and maybe don't have enough natural insulation. Plus I tend to be warm, especially in the AM after 2 cups of coffee. But it's not a deal breaker and they work fine. Added bonus: If you sneak and turn on the passenger side, it's fun to wait & see how long it takes the passenger to notice that their butt is on fire. Not recommended if you're in a relationship with the passenger.

Navigation: I don't have it but looked at it closely. It seemed similar to the system in my previous Toyota Prius. If you are going to use it, it's nice to have but I almost never used it in 2 1/2 years with the Prius. If you've never had a hybrid, the displays are useful. It's expensive and only a good value if you're going to use it and want the power displays.

As with any hybrid, the FEH is affected by cold, high speeds and loads. I do a lot of mountain biking and only got 24 MPG on a trip to the Western Slope with 3 bikes on the roof, 3 guys inside and lots of camping gear. The same drive with 2 people and regular luggage with no bikes on the rack, and I got 30. It did pretty well on the passes, even loaded down. In our current nice weather, I'm getting 29-31 in regular driving.

The interior can get uncomfortably warm at stops in traffic unless you defeat "ECON" mode. I have a feeling I'm going to be taking a hit on MPG now & then if I want to stay cool. I don't mind it alone but I'll probably be turning ECON off if I have passengers.