I'm really liking Slic3r 9 and use it the majority of the time.
I feel the cooling settings should be under the general print settings. I find that different objects require different cooling settings, so I'd like to be able to save cooling settings in the same spot as the rest of the object-specific parameters (like perimeter speed, layer height, etc)
I know different filaments require different cooling as well but I think moving cooling to the print settings would be all around more convenient and beneficial.
Otherwise I love slic3r!