I am using this iball Nirantar UPS-621V in my office since 4 years, it works very nice, it gives power backups for almost 25 to 30 minutes,
It charged very quickly, cost is also acceptable, the best thing is that it is not very heavy weight like other UPS, as compare to other it very light weight and easy to adjust in small places also.
I just put this UPS below the computer table and run my LCD and CPU. it controls the voltage automatically so that it protect computers mother from short circuit due to over load of voltage. it prevent my data from lose while power fluctuation. i get the time to save my data and shutdown the pc within the time.