I don't know how much power my system consuming and My UPS also behaves in a strange way. So I googled and stopped at Ubuntu Power Management. Installed powertop and everything is fine.
As mentioned in wiki documentation if I use sudo pm-powersave true it will enter into low power mode, so because of doing like this I can save some power but is there any type of problem I am going to face?
Bottom line, is there any disadvantage now or in future if I turn on low power mode?
I don't turn on low power mode in case something depends on reported/base clock versus actual clock with power save. Example: VMWare will warn you if the two are different.
This is also a good reason not to underclock video cards and whatever else. You can get "weird" problems that you can't pin down.
That being said, you're probably fine.
If you wanted to do gaming or high performance computing/number crunching, anything that tries to absolutely utilize hardware, then it's probably best not to use it.
In the case of multimedia there may be highly optimized decoders that experience bugs under power saving modes.
So low power mode is best only for general operations.
