Improved clinch, but.....
I use the knot for the situation. Most times, an improved clinch knot for tippet-to-fly is a good knot.
I recently read an article on fluorocarbon, where a "premium" company did extensive testing (very scientific, using an Instron recording tensile tester), and they specify a standard 6-turn clinch knot as being the strongest. They also were very specific about wetting the knot, and pulling it tight with a "jerk" (the action, not your fishing buddy) for best results, as it is very susceptible to thermal (friction) damage. The results were also very repetitive. I now use that knot for fluorocarbon, and have found that it is a good knot for the application.
Interestingly, they also recommend the four-turn surgeon's knot for attaching the fluorocarbon tippet to the mono leader. It works well, using the wetting/tightening action described above. Prior to that I had problems with tippets breaking at their junction knot.
I also use other knots for specific applications and other types of fishing.