What exactly do you mean by not so professional as compared with Canon, Nikon and other professional producer? You mean they didn't produce DSLR... wait... they did, only they stop that line sometime ago. They produce good PnS that are very very innovative and produce excellent results as compared to other big players' PnS.
It is all up to the target market. Fujifilm was not targeting at DSLR user when they design their cameras. But their cameras are by no mean not professional as compared to equivalent group of cameras from other major manufacturer.
And X100 is a rangefinder (with a APS-C sensor), I would say it is a very very good camera. The only quirks I have is its price and fix lens. And I would say, it certainly is very professional...