I have TIME ATAC Alium pedals, the cheapest ATAC pedal you can get but with just the same technology as the carbon version. They are 1g heavier than Shimano 515s and much, much better than any SPD-system, especially if you are riding muddy trails a lot. They leave the foot much more freedom than SPDs which is very good for your knees and there are no accidental releases at all. There is only one thing to remember when using these: the heel leads if you want to unclip. Money well spent.

They are 100% snow proof! I walked over a mile through knee-deep snow with them and they still worked fine.