I've had the trousers for a couple of years, they have removable knee armour, braces, waist adjustment, zip and velcro boot openings, removable thermal lining, 2 side pockets, zip fly and a zip to attach the jacket.
They have been waterproof for the rare times I've seen rain in Norfolk (honestly!), are comfortable, fit nicely without bellowing in the wind or cutting off blood supply. The boot zips don't catch on the lining which lots of trousers do. The elasticated waist is secured by press stud and hook and braces make sure you don't end up with a draft up your back.
The thermal linings are warm and easy to remove once the weather improves leaving tough textile trousers.
For anyone with worries over the strength of the material, I selflessly threw myself down the road admittedly only at 10mph but my lower leg took the full slide under a BMW and the only damage was a slight fraying of the material where the metal boot buckle was behind it. They did not even wear through there but I suspect they would do with a faster off.
They also look far better than you would expect from a budget pair of trews, black with expander knees and reflctive piping down the leg.

In summary, they are warm, strong, waterproof, comfortable and look good.

So why would anyone spend four times this much on a pair of trousers when these work this well?