I watched ESB a couple days ago, and if I remember the battle right, Luke jumps from an AT-AT in full gear just before it explodes, no rope or anything. Okay, he has the force, but the point is, they can’t be that high up. Certainly a rope should work. Incidentally, the AT-AT may be less agile than a helicopter, but by the same token, it will be much more steady, since it’s actually touching the ground.
Everything you ever wanted to know about AT-ATs can be found here. They estimate the height of an AT-AT to be 22.6 meters, or 74 feet. Luke fell from about half that height, which works out to around 3 stories. A rope would work, and the site mentions that among other methods, but I still wouldn’t want to fall that far.
The problem is that we have never seen the AT-ATs used as transports. I just figured that troopers repelling down would work. How high are helicopters when soldiers do today? I also don’t see why the AT-AT couldn’t kneel down like a camel (other than they may move too slow).
My theory on Star Wars-physics shields is that they’re designed to stop stuff traveling faster than a certain speed. Lasers and other projectiles as well as high-speed ships would be stopped, but a human or a walker could pass through easily. Note that they had to drop the shields to allow the transports and X-Wings to get through.
It’s sort of like the difference between getting into a pool via the steps or via a high-dive bellyflop.
Good point. In TPM the droid army was able to walk through the shield that was protecting the Jar-Jars.
Seems that those solar panels on TIE fighters would be especially susceptible to harsh winds.
As far as the AT-STs are concerned, from playing Rogue Squadron II on the Gamecube it seems like they’re loaded into barges and then a trooper transport ship (as seen in the special edition of ANH) takes them to the planet’s surface where they unload.
The look Obi Wan (ex-fighter pilot) gives Solo when he mentions the Kessel run shows you its BS, Solo then has to back down and just says, “Yeah, its fast enough for you” (or words to that effect) realising his bluff was called 
I’d think the X-Wings would be made for atmospheric flight. Wings are useless in space except maybe to keep the blasters at a nice wide area.
The manual for my copy of X-Wing on the PC (which is canon!) stated that the wings are used to house directional thrusters, whether or not they have any aerodynamic advantages is never shown.
Cold would actually be a much larger problem on a planet than it would in space. Heat needs a medium to conduct it away from an object. In a vacuum, there’s nothing to conduct the heat away, so objects would tend to retain heat better than they would in a sub-zero atmosphere. A ship designed to protect against the rigors of space is not necessarily protected from freezing planetary conditions.
Also, in a cold atmosphere you have the potential for ice forming on various surfaces, causing mechanical problems.
As for X-Wings, the wings aren’t shaped or placed properly to provide aerodynamic lift; they’re flat, too far back, and too small.