I bought a X-pipe a while back to use on my current project. It will be several more months before I can say anything about how it runs but here's what I found when I mounted it to my '78 750 parts bike:
It is not a 1 piece unit. It comes as four loose header pipes and a collector. It is up to you to weld or bolt the pipes to the collector once it's mocked up. As QTRHOSS states, it is held to the bike only at the header bolts so the collector kinda droops at the rear too much and there is little ground clearance. There is a cross bar on the collector and I intend to have a bracket made to attach the collector to the centerstand mounts. Some bending of the headers may be needed as it will still hang pretty low in the rear, even with the bracket.
Don't know what kind of metal the pipe is made of but it comes coated in a thin layer of crap paint. I imagine it would rust up pretty quick so if it's worth keeping I'll have it ceramic(?) coated.
I am the curious type and intend to find out how this pipe runs compared to the 4-1. But if you want a good, proven exhaust that you don't have to do a lot of work to make fit then buy a Kerker. They run really well on these bikes, sound great, and there are three baffle choices besides the stock baffle (loud, louder, loudest -or- fast,faster,fastest depending on your perspective)