fabien says: "Well, this post is quite dismissive"

Worse, this post is outright wrong.
It it currently 40 below here in Fairbanks, and I use my Prius for my daily commute as well as weekend trips into the mountains. I've logged thousands of miles in sub-zero temps in the Prius. Let's see:

"Gas economy goes down as much as 50 %"

More like 30-40%, as a result of the engine running more often to keep warm, which makes for cleaner exhaust (which the Prius is programmed to prioritize over fuel mileage). So? I'm *still* averaging 35mpg...

"and the batteries need to be trickle charged"

I don't even know what you're talking about here. You don't have to trickle charge - or *any* kind of charge - the batteries. That happens as you drive the car, through excess power produced by the gas engine, and regen braking. You never have to 'charge' a Prius under any conditions. It doesn't work like that.
Since the gas engine runs more often in cold weather to keep the cats warm (as mentioned above), you actually end up with the battery having a higher than normal level of charge no matter what your driving style.

"or the car does not run on the electricity if there's not enough power-due to the cold."

Again, hard to make sense of what you're saying. The car is not designed to 'run on electricity'. The electric motors are to *assist* the gas engine when power is demanded.

"The tires don't grip and you feel like you're driving on ice all the time."

You can say the same thing about virtually any car or truck on the road that is running on all season tires when it gets cold. Get some winter tires.
I've found the stability control makes the Prius extremely sure-footed on snowy roads. As much as my AWD Subaru (taking off on a slick surface is a different story).

"He hit a few snowbanks simply slowing down at a stop light."

Your friend needs to learn to drive if he's just going around sliding through stoplights and bouncing off stuff. He's dangerous. That's not the car's fault. Many people drive Prius's up here without that problem.

"winter put a lot of wear and tear on the vehicle and required lots of maintnenance. Electrical parts were frequently replaced."

[citation needed]

"If you get stuck, there's no horsepower to get you out!"

More horsepower to spin your tires faster does not help you get unstuck. What the Prius lacks in the 'getting unstuck' department is ground clearance and AWD/4WD. The overly sensitive traction control does not help. But it's not really an issue since the Prius is so good at not-running off in the ditch in the first place.