For the most part Fuel has stabelized, which is why we felt it was time to release a first beta a couple of weeks ago. Most of the framework will only be bugfixed on the road to a 1.0 release.
Having said that, we're not feature complete and some parts may still be rewritten, removed or added.
For a business solution my own approach is as follows: for any long-term projects (development time expected more than a month) I use Fuel and I keep bugfixing while implementing. For any short-term projects I still use CI or other solutions.