A specific situation in which I have found SOLO useful
I introduced an S2 (year 9) maths class to the SOLO diagrams and the language of SOLO, prior to giving them some nrich problems to work on in groups. My description of the task was for them to 'do some mathematical thinking' using the problems as prompts. I used the SOLO levels to give them a scaffold. When discussing their thinking, I asked them 'what level do you think you are working at now?' and 'what would you have to do to move to the next level up?'. Many of them found this very useful - for example they saw that to move from relational to extended abstract, they would have to generalise, make some predictions, make connections with other mathematical topics etc. and they then did so. I'm not sure how I could have given them this scaffold without some common language like SOLO or Bloom's taxonomy. I prefer SOLO, but I'm know people find Bloom's useful. It appeared to me that the language of SOLO created in the minds of youngsters some clarity about how to engage with a problem in increasingly deep ways. That seemed to me to be a good thing.