First the Pros, then the Cons
LOVE the CP3.0 High Output batteries!
Currently own multiple 2.0, 6.0 (HO), 8.0 (HO) batteries + previously owned 1.5, 3.0 (XC), 4.0, 5.0 & 9.0 (HD) batteries
Of all those batteries, the CP3.0 is my FAVORITE, which is why I bought 6 of them
The newer 21700 cells (in all the High Output batteries - CP3.0; 6.0HO & 8.0HO) are incredibly powerful
The CP3.0 works great on every M18 tool I own - including my 7-1/4" circular saw AND 10" Miter Saw (although I usually alternate between my 6.0 & 8.0 for that)
Being so much lighter than its' equally powerful/longer lasting 6.0/8.0/12.0 counterparts, the CP3.0 allows me to work faster and with less fatigue
The CP3.0's slightly longer and wider form factor is a much more stable base for my Impact & Hammer Drivers, especially when I've got a large and/or heavy bit in the chuck
Older (original) style tool belt-clip will not accommodate the wider form factor. HOWEVER, ALL my my newer tools come with the newer & belt clip that will accommodate the CP3.0 AND the Milwaukee service center in Denver supplied me with 4 more belt clips FREE OF CHARGE (for my tools that didn't come with the newer clip)
The previous reviewer that complained the he "Had this product for just over two years, hardly used them and would not charge at all" doesn't know/understand that ALL batteries are capable of (temporarily) loosing the ability to charge if they've been unused for a long period of time and/or been stored in very hot/cold environments. In that case, the Milwaukee "standard" charger () WILL NOT charge the battery. However, the Rapid Charger often will. If that doesn't work, a Milwaukee Service Center should have a charger that will recondition the battery so that it can be charged and used as normal (I've had 4-5 batteries that the Service Center in Denver, CO "rescued" for me.