Yep as Brian says
I have run my 2K2 Cocker on Co2 for nearly a year with no problems just make sure it has an anti-syphon tube fitted.
The only real problem I experienced was having to chroney a little lower because of spiking with Co2 with jumps of +/- 10-15 fps
but this can be over come by double regging with something like the female palmer stabalizer which does two things the palmer will stop liquid getting to you second reg and supply it at a constant pressure so Co2 spiking should not become a problem.
But in the long run if you can move to air it is worth the extra money up front and with preset regs getting cheaper and more sites offering air its only time before it hopefully becomes a standard.