Feedback on my winter backpacking gear?

Kevin, to be helpful we'll need to know where and how you're going in the Sierras this winter. Given the overall tenure of your post, and the fact that you're planning on snowshoeing, I assume you don't yet know the answers to these questions yourself and will spend the winter finding out. That said:

-Stay away from avalanche terrain. Learn enough to know how to do this. It will mean lower elevation terrain, which will make it possible to use your hammock.
-That said, I'm not a hanger myself, but I can't think of a shelter which would work well with both a wood stove and a hammock. You'll loose a lot of the heat with an open tarp, rather than the pyramid shelters traditionally used. If you plan to expand your winter skills for years to come, I'd get away from hanging. Not so good above treeline.
-Opinions vary here, but I don't think hard shells are a good idea in winter. Sometimes they're necessary, but if you can get away with a more breathable windshell you'll be happier in every way.
-No need to wear mountain boots unless you're climbing ice or steep snow. They suck to hike in, and there are more appropriate options which are just as warm and cost less than half as much.
-If you have any questions attached to an ice axe, don't buy one or get near anywhere you might need it.
-The Frostline has a rather low fill/overall weight ratio. There are more efficient warm jackets.

My plan is to stay below tree level (since I'm a hammock camper and need wood for my stove).

I agree WRT avalanche terrain and I plan on staying clear.

– WRT shelters for my hammock, there ARE people who have rigged REALLY nice hot tents with hammocks but I can't find someone who actually sells a tarp pre-setup for this usage. I may have to install a stove jack myself.

– I don't really like being above the tree line. Even if I DO intent on going above the tree line it would mostly be to go over a pass to get to more trees… and if I can't make it in time I can always did a snow cave.

And thanks for the feedback!!!

* Here are some hammock hot tent ideas:
http://www.hammockforums.net/forum/showthread.php?t=40574

* Try to find a group or at least one person to go with if you can. If not, at least carry a PLB.

* Be careful relying too much on wood for heat, cooking, and melting snow. Much of the down stuff will be hidden and soaked under the snow. If it's a popular camping area, then burnable wood will likely be scarce anywhere near the campsites. You might want to think about an inverted canister stove or a white gas stove if you're going out colder than an inverted canister will function.

* Don't spend much money until you've been out in the winter at least once. Try to adapt your 3 season gear as much as possible, and only purchase the gear which you just can't get by with in the cold. My in-camp insulation has been a synthetic casual parka which I wear to work on colder days, but just last year I upgraded to a $24 down discount store jacket. Check thrift stores too.

* Once it gets around 24F or lower, I definitely prefer a softshell because the snow is drier. At that point, the main source of moisture becomes perspiration rather than precipitation. Softshells let out the perspiration better.

* Testing gear in the backyard or while car camping is time well-spent. I'm always surprised at the mistakes I avoid.

My experience comes mostly from backcountry skiing without a hot tent but I would want more mid layers and liner gloves for even a day trip. I generally bring 2-3 pairs of liner gloves (ibex knity gritty, or 100-400 weight fleece, rab powerstretch etc) so I can change them out as they get wet from snow and sweat. I might throw a pair of leather palmed gloves (kincos insulated work gloves are cheap and preferred by ski lift workers, rab makes some thin leather palmed softshells) in if you are going to be handeling a lot of wood etc.

An uninsulated mitten shell + insulated insert that can be worn over your liners together or (more frequently) independently is also nice I take she sells on and off over my liners (and store them in a coat or on my ski pole handles) while hiking and use the insulated inserts (by themselves at rest stops). You can even use wool socks inside the shell if needed. I don't have any experience with the dakine mittens you have selected but i would make sure they have an uninsulated shell plus mitten (not glove liner) roomy enough to work with liners.

I agree with the others about softshells vs hardshells. Even in near/above freezing temps in the cascades I would often leave the hardshell at home unless the forecast called for heavy rain and tend towards some combination of thin softshell, griddy fleece (patagonia r1) and/or windshirt as my "action suit." Baselayer alone is often too cold and baselayer + hardshell is too sweaty. I really like my rab exodus pants in particular because of the thigh vents…being able to regulate temperature without stoping and adding/subtracting layers is nice in winter.

A thin synth poofy might also be a good addition. You could wear it while gathering wood and dealing with the fire as it won't matter as much if you tear or burn it and save the down poofy for trips outside, fireless rest stops etc. If you are towing a sled instead of wearing a pack you could even take it off without a full rest stop to temp regulate.

For trailhead access use get snow chains that you can put on your car quickly without driving forward onto them (ie http://www.amazon.com/Thule-Quality-Passenger-Chain-090/dp/B000UNRJD8). That way you can put them on while stuck instead of having to mess around trying to back down the hill to a place you can drive onto a pair of cable chains.

Finally, for avoiding avi terrain and gps use check out the slope analysis tools on my mapping website:
http://blog.hillmap.com/2012/01/slope-overlays.html
http://blog.hillmap.com/2012/03/caltopo-layers-gpx-import-embedding.html

(If you don't know what an overlay highlighting >30 degree slopes is for seek some avi education…even a free avi awareness lecture to start and "Staying Alive In Avalanche Terrain" is an engaging read).