The X100 really has impressive metrics for a compact camera. Its sensor manages to outperform that of the Sony NEX-5, and thus takes first place in the mirrorless rankings. The interesting part though is that it also manages to outperform or rival mid-range DSLRs such as the Nikon D90 and the Canon EOS 60D, thanks to its well-handled noise and good color management, but above all thanks to a truly decent low-light performance. 
Previously Sony’s NEX-5 had already threatened some DSLRs in performance quality, and we now know for sure the X100 goes even further. 

It remains to be seen if the X100’s sensor performance can help it overcome other negative points in categories such as: video function, fixed v. interchangeable lenses, and overall speed.
On a side note let us not forget that no matter how good the X100 might be, the latest generation of Sony 16 Mpx sensors that powers models such as the K5, the Alpha 580, and the D7000 is still far better; especially where dynamic range is concerned. On the other hand, these models are still far more expensive.

FujiFilm X100 vs. Nikon D7000 Dynamic Range
FujiFilm X100 vs. Nikon D7000 Dynamic Range

If we take only sensor performance into account, the X100 is a success and we’ll even go as far as to declare it the perfect everyday companion for the DSLR enthusiast.