hi mate, i have one . good gun light, accurate but expensive to run. i brough i BSA Lightning 7 months ago, and would not look back. The umarex is expensive to run, Co2 being about £10 for 100 shots, and there not that high powered, to save Co2.Also like you mention it effected by the cold, so when i am walking around my range and zero is effected. Personaly i would go for spring or PCP. However if you like Co2 guns the umarex 850 air magnum is one of the best on the market. I would say, if your desprate for Co2 go for the umarex but other wise its spring or PCP for me.