Insulation:
There is no denying that warmth and comfort will affect your mountain experience. For warmth one will have to start with well insulated clothing.
Two major insulations stand out, natural (down feathers, cotton and wool) and synthetic insulation.
Down feathers are typically restricted for use in jackets. Common synthetic insulation includes fleece, Gore-Tex, Climashield and DryTec (Mont-bell) which can be found in many ski garments.
Hood:
The choices here are limited to insulated and non-insulated.
Typically we get our insulation from our hat, headband or helmet.
On deep powder days or rainy days a hood will keep you dry.
Pockets:
Jacket designs these days include many pockets. Back country skiers will appreciate a large chest pocket for a radio and shoulder attach point for a microphone..
Many jackets will come with specialized pockets for lip balm, trail maps, goggles, mountain pass (clear pocket), cameras, cell phones, wallets, etc.
Sleeves:
Two features are often associated with sleeves, removable or arm pit vents.
Either way, the idea here is comfort during spring skiing.
Powder resistance:
Some jackets have features to keep powder snow out of your jacket.
Chords and straps which can be tightened around the bottom of the jackets as well as the sleeves, may do wonders to keep out the snow.
Waterproofing:
Most winter sports jackets are water proofed. It is the older jacket which loses its waterproofing which causes trouble.
Products like 3M Scotchgard can return ski apparel to its original waterproof condition.
Heated Fleece/Jacket Liner: Karbon has a new electrically heated fleece for their 2010 line-up. The heating wires are "printed" onto their fabiric and integrated with the fleece.