I have now used this tool to dispense over 400 tubes of Sikaflex polyurethane caulk during the construction of my house, and boy, has it been terrific! Not only can I not imagine having to push all that caulking out by hand (then I could add carpal tunnel syndrome to my tendonitis and "tennis elbow"), but the tool has done the job quickly, accurately, and reliably, despite becoming increasingly gunked up with the caulk thanks to some bad tubes that split with the plunger inside, leaving caulking all over everything.
On top of all that, it's miserly with the battery. I can't have changed the battery more than 3 or 4 times during the whole process (beginning in May), and then never because it completely ran the battery down--more like I said, "well, it must be time for a new battery, so I'll stick one in".
The variable speed control works very nicely and can help prevent making a huge mess in tight areas or when small amounts of caulk are required. You can tune it down so that it barely pushed the caulk out, giving you excellent control.
I'm very impressed and highly recommend this tool.