I have a skilter 400 on my 25, and it seems to be ok, and the skimmer seems to work decent, however the skimmer is LOUD. The tank is in our bedroom, and we have to turn the skimmer off at night. I believe the intake tube to the filter is too open, cause it doesnt cause much current around it, and I have see food flakes and stuff come within 1/2" from it, and float right by. I am thinking about modifying that part of it, to see how I like that. Also, i dont really like the skilter media, and its not easy to find locally. I've been using just floss pads and a bag of carbon in back, which seem to do a good job.
I also have a bak pak 2r and it does skim more that the skilter, and isnt as loud(still noisy, I used a bubble stone on the air line to quiet it a little) but the output was too big to fit between the edge of the tank and the glass top, so I bought the skilter to use instead.
I think for 45.00 the skilter is not a bad unit, but if you already have a powerfilter, you would be better off getting a bakpak. I picked my bak pak up for $50 used at a LFS.