Short answer: yes
Long answer: also yes but with the caveat that different manufacturers are better than others. For example, I currently have a Tokyo Marui M9A1 which is one of their more recent designs with a larger blow back unit for more snappy pews. It works quite happily in cold weather and shoots quite nicely. I used to have the SOCOM Gear M9A1 which was all metal, with the lower rail and looked great, but leaked gas like a sieve and maybe got half a dozen rounds off before completely degassing IN THE SUMMER!
In summary, get the TM M9A1 and enjoy pwning n00bs.