Can you explain what's wrong with "la kato"?

I think one of the advantages of learning esperanto is, that you can reuse the learnt vocabulary in other languages (from the romanic or germanic familiy). So you don't really lose the time even though you might not use it in your everday's life (which is possible though).

Going to esperanto meetings is fun. I never met so many interesting people gathered in one place. But it's probably also true for Lojban that it attracts smart people.