First, a little bit of my background....
Home based DIY'er, with a penchant for spending way too much money on tools.... I have a Nissan Titan that I do most of the work on myself, and an 83 CJ7 that I do 99% of the work on myself (with help from friends.) I also do quite a bit of tinkering around the house... hanging towel rods/pictures/etc. And have some bigger projects coming up.
I had been looking for a cordless impact wrench... mainly for convenience sake. I have a dewalt compressor (just one of the $300 home depot jobbies,) but when all I'm doing is popping wheels off to do brakes or something, it's a pain in the *** to wheel it out, plug it in, run the hose, etc. etc. so I was looking for a quick and easy cordless impact to make life easier.
A couple months ago, when the C3 went on sale for like $105 or so, I picked it up, in addition to the $90 drill that came with the Li-Ion battery and charger (mainly for the battery.)
So, for $200(ish), I've got the drill, the 1/2" impact wrench, 2 ni-cads, one ni-cad charger, 1 li-ion, and one mixed chem charger. I've also picked up the job light, as well as the tire inflator.
Sure, these aren't the high end tools some may be looking for, but they've been perfect for what I've needed them for. I also have the M12 Drill, impact driver, and voltmeter, as well as a Dewalt 18v drill that I picked up on some screaming deal. But to be honest, the C3 set has become my "go to." The drill's got every bit of power I need (I'm currently hanging Gladiator storage in the garage, and it's been my go to tool there.) And the impact popped lugs no problem. The inflator is a great tool to have in the tool box when out off roading in the CJ, and the job light is just useful in general when under the truck.
The M12 is great from a compact standpoint (I keep it all in one little bag that I'll grab when going to help out at someones house or something,) and the Dewalt is great for big jobs.... but at the end of the day, the design of the C3 system, for my use case, is pretty spot on. Some of the other things I plan on picking up include the leaf blower (way easier to carry on the roof to blow out gutters then the gas one) and the circ saw (although, may look for an 18v bare tool deWalt for that instead.)
My personal opinion is that, as long as Sears continues to support the C3 line, it's a pretty spot on product line for the home diy'er/tinkerer.