Overall no. It has good OS and is capable of good images, but so is the 100-400. A lot of people love the Sigma, more people on this site love the 100-400.
I've tried both of them and I prefer the 100-300mmL to the other two.
It all depends on what you like doing and what you shoot the most. Unless you go hiking and wildlife watching every weekend, you will get more use and see more benefit in the EF-S 17-55mm that you are dicussing on other threads.