does this work on pilled furniture

I am sorry to say mine NEVER worked at all ! There is a BIG problem with the wire on the plug in ,it keeps going off every 2 seconds and batteries do not fit where they are supposed to go! But I bought another brand and it works great! ( oreck) Now if I could just get my money back?????

Is the power supply 120v (U.S.) or 230v or universal?

It's 110V 60 hz only. The power supply is built into the plug

how do I open battery compartment? It says this is dual powered but I can't figure it out...

Remove lint holder and the battery compartment is visible there. I also received a cord that allowes me to use AC or DC.

Description says "2.5 inch shaving surface" but not whether this is circumference, area, radius or diameter. Which measurement is this 2.5 inches?

The surface of the saver that would come in contact with the material has a DIAMETER of 2.5 inches, however, the cutting surface, that is the area that the blades would be able to shavethe material is about 2 inches in diameter. So far, the shaver has worked well on the pants and sweaters I have used it on. Per cautions from other customers...be patient, take your time,don't try to press to hard to force it or you may cut the material. I've had these types of shavers in the past, and this one seems to be the most powerful, and it is larger that others I've had.It will clean up those "fuzzies" that make your sweaters & pants look old before their time..and give them new life....but again, be patient with it...make sure the surface is flat and supported underneath, ( I do it on my ironing board) and keep the surface as smooth as possible. Hope this info helps. Ann