In reply to IoanTataru:
I imagine this is a dead topic.
But ... the Lowe Alpine sacs have this buckle and I find its very easy to use with and without gloves on. The plastic buckles I have on a blue ice pack are a pain as its hard to squeeze them with gloves on, especially if the temps are low making the plastic stiffer, but the space you squeeze is just a bit too small.
On the other hand Alpkit use similar metal buckles on pads and they are a pain because of the lip design which adds security but means you have to guide the nylon over it each time - a 2 handed faff. So I guess in the end it comes down to design detail with metal or plastic buckles - I can't speak for the Montane design.