I have the Oceanic BioCube in my office, I love it. The only problem that I had with the BioCube was the fans. After a few months they started to make noise, BUT They replaced them no questions asked. I did replace them again last year to a slightly higer volume fan, but that was my choice, their fans were still ok. I added the Nanotuners light upgrade & I wanted to have larger fans. By the way, I highly recomend doing the Nanotuners light upgrade.
As far as a skimmer, I dont belive you need a skimmer for a nano tank if you do your water changes like you should...every 2 weeks. There is not enough there to skim, the water changes will take care of it.
The only thing that I can say that I dont like about the Oceanic BioCube 29 gallon....is the lid is not on a hinge, NOT sure why but its not. Go to your LFS & lift the lid......if you dont hold on to it, its going on to the floor.
Good Luck