It all depends on where u want to work, what do your prospective clients use?
Here in London most of the broadcasters are on AVID ( 3.5, 4.? and 5.0.3) (at present 5.5 does not work with EVS transfer managers)) , (with a few still on FCP 6 or 7.)
I am not sure where the FCP users will move to if at all.
Not in my opinion FCX unless the many missing "broadcast editing" features are added soon.
Now that I have MC 5.5.3 ( works with Lion, but not servers at present, you need to boot into SL for network connectivity.) on my laptop, I shall be looking at broadcast input/output options as it looks as if my Motu v4hd died with fcp. Possibly an aja solution, I shall then offer MC editing at "home", instead of fcp.
Since both Avid and adobe are doing offers at present, I now also have Premier5.5 just in case!