AIUI - and I'm not an editor - there are still woeful issues with audio track control and group working across multiple edits.
The FCP X issues are causing many of the firms who moved from Avid to FCP 7 converts to go back to Avid. FCP started taking over when it became a real contender to Avid. There was a time you could get a decent SDI FCP editing system for £4k yet the Avid equivalent was almost three times that, and that was even Avid Xpress never mind Media Composer. Avid tended to stick to it's own hardware, so that meant drives, I/O (Meridian) and all sorts of extra rubbish.
Now it seems Avid have opened their eyes and dropped the price, custom hardware requirements and are chasing the FCP converts who are due for an upgrade - with many going back to Avid.
FCP never had a decent 'media sharing' which many broadcasters now rely on. There were workarounds, but FCP X has pretty much made the whole concept of shared storage null and void for now.
I've been using both for years for broadcast work and have no real preference. I tried FCP X recently and despite it looking nice and shiny with a few nice features - it's still rubbish for the pro user delivering broadcast output.