Klingon is deliberately hard. The creator said so and the people who promote it say so. Mastering it is a more a feat than anything else, for people who are drawn tot that sort of thing. It's realistic feasibility as a widespread, useful language is, I suspect, low-to-zero (most probably zero).

I know that in this pragmatic world what I am about to write may find little echo. However, I do believe strongly that Dr. Zamenhof put his heart and soul into Esperanto AND his work for international understanding. He created Homaranismo after a great deal of thought. He was a very learned man but also a man who devoted himself to human health (he was an ophtholmologist). He was religious without being a zealot - the kind of guy who would sit you down and take you seriously, more seriously than himself. I am sure that he was a wonderful father and uncle. His language, OUR language, breaths - it has a heart: Ho! mia kor'! This is what was missing in other languages. Klingon, from what I have learned, is maybe the language of angry people. Who wants to be angry all his/her life? Ido wants to be "little French" - sa gloire est passee. Other language inverntors invented a language as a THING, a mere TOOL for literal understanding. Esperanto - with its "-um-" and "je" allows for human error, which is why we like handmade goods more than machine made goods. Esperanto has its little imperfections but it was created by a master of the art, a knower of the human condition. A language without flaws would not be a human language - and yet, we remain humans and shall, I hope, always remain humans and not machines.