I justified my dismissal on the grounds that they looked heavy, expensive, and not very waterproof. )
It's completely waterproof. I've never had any water issues with it. I don't think it's that heavy.
It is quite expensive, but I've had a lot of use out of it, and I've never regretted the money I spent. The fixing system is really excellent. Once on the bike, you're not really aware it's there.
I used to put my U-lock in the waterproof pocket inside the top flap before I began leaving it where I park.