Woodrow, you're calling that an impact wrench, but the link you provided is a ratchet, not an impact. I have the 1/4" and 3/8" M12 ratchets, and the
"Insider" M12 ratchet, which is good for really tight access situations. I don't use any of these on a regular basis because I'm more of a "loosen with a tool, but tighten by hand" feller, and impact works better for loosening. I could probably live without them, but I don't have to, so I have them.
I also have the
3/8" M12 right-angle impact, which might be what you're actually wanting? Now that tool, I wouldn't want to live without, due to my aforementioned methodology on loosening/tightening. It's got serious torque capabilities, especially considering it's a right-hand drive tool. It's also very hefty. Probably weighs twice what the M12 ratchet does.
Finally, with regards to having to deal with another battery. It's inevitable. Milwaukee only makes certain tools in the M12 series - ratchets and right-angle impacts being just a few. I also have two generations of their rotary tool*, a right angle drill, a 3-plane laser level, and a rivet gun. All but the rivet gun are only available in the M12 series. The M18 rivet gun is a lot more expensive, but it can do 1/4" rivets (the M12 is limited to 3/16" rivets).
*
Of all my Milwaukee stuff, the M12 rotary tools (I have two - the current gen and the one previous) are the only ones that have disappointed me, and I can't recommend them. My issue with them is that in hot weather, which is common down here, they won't run continuously with moderate loads on them. I can run them for about a minute, and they shut down due to an over-temp situation (I think). I then have to let them cool down to use them for another minute. I've taken to blowing compressed air through the cooling openings to get them cooled down. It's ridiculous. I ended up buying a pneumatic Dotco pencil die grinder, as recommended by Mike_H way back on Page 12. It's not cordless, but it just runs and runs!