There is some internal functionality for algorithms to send out-of-band progress information to the user interface in v2, but it has mostly been to experiment with it and see what we need. Only the meld algorithm really uses it at the moment. I am not sure we have converged on the right mechanism yet, hence it hasn't been included in other algorithms.
The problem is, as always with logging, that you do not want to log too little, but you also do not want to log too much. However, this distinction is very much a function of the problem you are solving: sometimes you want to see an update for all terms canonicalise acts on, but sometimes that's a very fast part of some inner loop and you are not interested in that. Some nested progress indicator is probably best.
If you have any good ideas, please post.