Cordless tools have come to far not to give them serious consideration. I believe there will always be a place for air, I'll be putting in a big compressor when I buy a house within the next year and running air lines throughout the garage, but cordless tools are fast encroaching on what was...
I've got both the 3/8" and 1/2" Milwaukee M18 cordless impacts. I keep the 3/8" in my truck and the 1/2" in my box. I didn't want to commit to air tools and a compressor being that I knew that I'd be relocating within the last few years. Best money I've ever spent and the portability is great.