A really awesome all around backcountry ski pant for ski touring is the Outdoor Research Trailbreaker Pants. Overall, it's got great functionality for backcountry ski touring at a price that's hard to beat and is really comfortable to ski tour with. It's got just about every feature that you'd want in a backcountry ski touring pant... side zips, suspenders, lots of pockets, beacon pocket w/ clip (or iphone pocket), wide boot cuff, insert for knee pads, soft shell, light weight... etc.
It's also the prefered ski touring pant that Lou Dawson of WildSnow.com ski tours in and is also used by K2 ski guide Martin Volken.
The OR Trailbreaker Pants has knee pad slots, so you can add Soft Knees easily by rolling them up and inserting them into the knee pad holder in the pants (you may need to trim a little bit off the edges of the Soft Knees with a scissor to make them fit perfectly)