To start with, the laser is very accurate. I performed an initial horizontal accuracy test and found that the laser was within 1/32 inch over 27 feet. The laser is big and heavy (compared to my 14 year old DeWalt DW087K red laser) - 2 lbs 1 oz with the 12V battery and no positioning device, 3 lbs 2 oz with the magnetic bracket, and 3 lbs 15 oz with magnetic bracket and drop ceiling clip. My DeWalt weighs in at about 1 lb 1 oz with 3 AA batteries and its permanently attached magnetic bracket (about the same as the Bosch magnetic bracket alone). The Beam - in side-by-side comparison with my DeWalt laser, the Bosch was noticeably brighter indoors on an overcast day with no artificial lighting. The Bosch beam was also a little thinner. I tried the Bosch laser with both the included 12V battery and the AA battery adapter. The 12V battery produced a slightly brighter beam than the AA adapter did. Bosch Leveling App - the Bosch Leveling app allows you to control which lines are on without touching the laser. This allows you to change which lasers are on and off, or put the laser on standby (no lasers on) without disturbing the positioning of the laser level. Sometimes the app doesn't "see" the laser level. I never quite found a reliable set of steps to overcome this problem, but turning the laser level Bluetooth off and on again, or killing the app and restarting it sometimes fixes the issue. Battery life - Bosch claims 6 hours of battery life with the included BAT414 (12V, 2.0Ah) battery, with all three lasers on, and Bluetooth off. I tested the battery twice with Bluetooth off, starting with a fully charged battery, turning Bluetooth on periodically, but only long enough to get a battery level reading in the Bosch Leveling app. Each time the laser level shut off at about 4 hours and 15 minutes - far from the claimed 6 hours. Each time, the battery level dropped to about 50% after only 1 hour, 33% after 2 hours, 29% after 3 hours, 20% after 4 hours, and the unit shut off 15 minutes after that. A third time, after charging overnight, the initial battery level was at 62%, so I turned the unit off. Two days later the battery level was at 56%. After turning the unit off and on again, the battery level was at 70%. Not only is the battery life significantly shorter than claimed, the battery levels reported by the app don't appear to give any useful indication of the actual charge remaining or how much longer you can expect the battery to last. I called Bosch about this, and gave them the serial number of the battery, and they claimed it was manufactured only 5 months earlier, and recommended returning the unit for refund or replacement within their 30-day money back guarantee period. I opted for replacement, and got almost identical performance from the replacement, which I also returned. This might not be a problem for you, but I think Bosch should provide accurate information regarding battery life. Positioning Device (mounting bracket) - the adjustment knob on the provided BM 1 positioning device allows up to 2-1/2 inches of vertical adjustment. The ceiling grid clip has two positions, raising or lowering the laser by another 1 inch. With this degree of adjustability, I was surprised to see that the horizontal line can go only 5/16 inch below the ceiling grid it's clipped on. This seems like a small distance to me, but I don't install drop ceilings, so this may be fine. I'm used to using my DeWalt laser by magnetically attaching it to the corner bead on finished drywall, making for quick and easy setup anywhere there's an outside corner. The Bosch BM 1 device also has magnets, but they're barely strong enough to support the weight of the bracket itself on a corner bead. A workaround (which I tested) is to use a metal strap (i.e. Simpson strong tie, etc.) attached to the wall with a large 3M Command Strip. This worked really well and seemed rock solid, but ads time and cost to setup, since Command Strips aren't reusable. CAL Guard - the CAL Guard feature is much too sensitive. Normal handling of the laser can easily trigger CAL Guard, leaving you to wonder if something has actually happened to cause an accuracy issue. The Case - the hard case has a formed place for everything - except the laser. The place for the laser is a big open rectangle. I find it odd that the most delicate piece of the kit is the most poorly secured within the case. Combine this with the CAL Guard sensitivity and you'll frequently question the accuracy of the laser.
