I have worked for years as pro producer-director using Avid, Final Cut Pro and Premiere. I am now retired but thought I'd dabble with the trial Final Cut X and perhaps buy it. I'd heard all the arguments about it but thought give it a fair try.
From what I can see, the only really big thing in its favour is the price. If you are a pro, used to the other editing systems my guess is you'll find the X extremely different. I have never sold my services as an editor but I have done an awful lot of editing. Quite frankly, I am willing to learn new tricks but not if they don't bring substantial benefits. I see far too many disadvantages and too few benefits to make the switch.
My short advice, for what it's worth, is if you intend to turn pro - especially as editor - don't even think about buying or training on FCP X. There is a very good chance you will regret it if you do. The price should not affect affect your judgement. If however you only intend to learn one system and you are an amateur (no matter how serious or "professional" your attempts may be) and money is a big deciding factor then go with the X. Of-course if you are taking the pro route there is then the old argument over Avid or Premiere but I'll leave that to others.