Thought I'd revive this thread as I purchased a new cordless impact and can say that they perform above and beyond my expectations. I was a skeptic at first and thought the best you could get had to be a air-based tool but how wrong I was.
I ended purchasing the
Milwaukee 2663-22 18-Volt M18 1/2-Inch High Torque Impact Wrench with Friction Ring from Amazon. This little baby was more than capable and a very good contender against any air tool out there. With this tool I was able to rip off the old suspension and install my RC 4.5" X-Series lift kit, pull off all my tires lug nuts, remove and replace all the nuts on transfer car twice without ever having to switch over to the second, included, battery.
Simply amazing! This tool has really changed my opinion of what the newer batteries are capable of. All you skeptics might want to have a second look.