This value has proven adequate for long-running programs with a relatively steady allocation rate. I'm interested in numerical programming. Here are a few. See also the discussion on the caml-list mailing list. These figures are geometrical means on a relatively small set of benchmarks.
Individual figures are much more contrasted.
On the Knuth-Bendix benchmark, which I consider representative of the typical ML program, the speedup is 1.85. In short, these figures don't mean much. O'Caml bytecode programs run 1.5 to 2 times faster than Caml Light 0.7 programs. If your program spends a significant amount of time in the latter operations, then the speedups obtained by going to native code are limited.