That's an APC Back-UPS RS series unit. It's line-interactive, so it has a small switching transient on a switch to battery power, but it can protect against over- and under-voltage conditions.
However, it's output waveform is a square wave, not a sine wave.
A better unit (though not as many watts) is the APC Smart-UPS SC620(http://www.newegg.com/Product/Product.aspx?Item=N82E16842101011&Tpk=SC620), which has a stepped-wave output. A higher wattage (but more expensive) unit in this class would be the APC Smart-UPS SC1000 (http://www.newegg.com/Product/Product.aspx?Item=N82E16842101131).
To get a sine wave output, you have to go up to the Smart-UPS or Smart-UPS XL units.
The names "Back-UPS", "Smart-UPS", etc. are just APC's marketing names for that line of products. In addition to better quality output power, the Smart-UPS units tend to have more features, like monitoring software, tool-less battery replacement, LED status displays, better efficiency, etc.
Thanks for the kudos, gents. I'll see if I can write something up that could be a sticky.