If you google it you will find loads of suppliers. As to whether it is more visually appealing or not would depend on what you are making and personal preference. It would be a bit of a pain to join wouldn't it - mitres and the like?
thanks lads!
it is a lot stronger than normal round tubing for my motor cycle racks.
certain bikes I can get away with minimal flat tubing's like my current bike the ER6F.