Pros: Went back to look when I bought mine, the invoice is dated 7/14/2010, so it has been over two years. I'm typing this review while my workstation and monitor are running off the unplugged UPS. The alarm is beeping and the transfer to worked perfectly. I'm not sure if the internal battery can be updated, I have to assume so. I was also curious about the transfer time so after two years I finally looked up the specs: Equipped with AVR (Automatic Voltage Regulator). Better protection ability Equipped with inverter, which yields less charging time. Transfer time: 2~4 ms. More energy efficient and cost effective than Off-Line UPS. Workstations and small to mid size servers. Originally I got this for clean power to my overclocked i7 EE. Now I am glad I have it after moving because the lights dim all the time. I got a smaller APC for the iMac.

Cons: Thing gets warm in the summer which is bad for my office because it is in the garage and not well ventilated. I wish we didn't have to rely on the software to get simple readout, but that's probably part of the marketing strategy to get you to buy the higher model.