Ive just decided to look into some type of nightvision and know very little yet.  My main concern that googlr hasnt helped me find is what is the real world performance of either a pvs 14 or some type of thermal scope in sub-zero winter mornings?

Most of the guys here like to use the Lithium AA Energizer batteries for the units for the long life, and the fact they work good in very cold weather with PVS-14's and other image intensifiers.

Some guys have used the units in -30 degree conditions, so it should work for you.

http://www.ar15.com/archive/topic.html?b=6&f=18&t=356097

Thermal, that's going to depend on the unit your interested in. Some do fine in cold weather, others might have issues to be aware of.  Most do fine when your using Lithium batteries to power them though.

ive had mine out when it was in the 20's

the battery wasnt new and i had some slight image flickering for about the first 20-30 seconds i turned it on, after the tube was running for a few minutes all was well.

also keep in mind, the military does not care how cold it is, it has to work.

Per the Army/AF/Marine Operators Manual the operating temp range is -51C to 49C (-59.8F to 120.2) and the storage temp range is -51C to 85C (-59.8F to 185F).

I've had no problems running a pvs14 right at 0F many a night.  3-4 hour outing, FLIR thermals as well.  The equipment functioned well and batteries outlasted my hands and feet.