I've owned my Milwaukee M12 Cordless Hackzall since almost the beginning of 2013. Since then, I've reached for the Hackzall more than any of my other saws and haven't used my corded reciprocating saw at all this year.
Every time I use it I'm blown away by how powerful this little cordless reciprocating saw is. Milwaukee has managed to squeeze a lot of power out of only a 12V Lithium-Ion battery.
Considering Jerome Schnettler and Edware Ristow invented the Sawzall (first reciprocating saw) back in 1952 for Milwaukee, it's no big surprise that Milwaukee would come out with such an innovative new design. Although it has the same shoe , uses the same blades and can be used for the same types of cutting activity as a reciprocating saw, it is a whole new type of tool.
While other cordless reciprocating saws merely tack a battery pack onto the back of a standard looking reciprocating saw, Milwaukee took a different approach with the Hackzall creating a compact reciprocating saw that can be used in a lot more places.
The variable speed trigger smoothly controls the speed of the blade from between 0 to 3,000 strokes per minute and a bright LED illuminates the cut area. Four red LED's next to the blade lock indicate how much charge is left in the battery. These LED's are activated every time you pull the trigger so you don't forget to check.
A twist lock mechanism provides tool free blade changes of any blades that will fit in a standard reciprocating saw. The blade can also be mounted in reverse. With the blade facing the opposite direction you can get in some tighter spots since the shoe is shorter on the back end.
Overall the tool is built tough and can handle a lot of abuse. I've used it for cutting 2x lumber, some metal pipes, bars and have used it extensively over the summer in the landscape to cut thicker branches that would have taken a long time to do by hand.
I don't know that I'd grab it if I needed to demo a large area (nor would I use any cordless saw for that) but for the occasional cutting job throughout the day it works well. The Hackzall would be a great tool for plumbers, electricians, etc to in their tool bag whenever they need to cut through framing. Great saw for the homeowner that likes to tackle weekend projects but tough enough to withstand daily use too. I've put the M12 batteries through some tough situations and they've held up. Other Li-ion batteries for other tools I've owned haven't done as well through similar use.
If you already own other M12 tools you can purchase the bare Hackzall without a battery or charger. If you don't, you can purchase the Hackzall with battery and charger. If you need more power, a slightly larger 18V Hackzall is available that uses the M18 RedLithium batteries.