I've been wanting a computer chair for a while. Tried a few in John Lewis. As OP'er i just use a dining chair at present, and its rubbing ruts in the carpet, with pushing back so was hoping to get a chair with sled like rails to save the wear on carpet. I have to try it for comfort though. I wouldn't buy without trying. I'm sure this dining chair is responsible for my neck muscles being stiff as hell.
If you get a standard office chair on castors, you can also get a carpet protector to prevent damage.