I used Slic3r before Simplify, and it has one majorly nice thing that I am missing a lot.
Notice how in slic3r you can have a filament name, and then have diameter, extrusion multiplier, and print temp. Great. As it should be.
Then you can have print settings - such as layer thickness, type of infill, type of support. Great.
Then you have your printer settings - one for each printer you own. Great.
With Simplify - these are all mixed together and inseparable. So with Simplify, I can't just have a "high quality 0.1mm slow print speed" profile, as I would need one for each of my filament types. And even if I could figure out how to setup the material change in Simplify, it would not be feasible to have more than one ABS setting. There is no way to associate the extrusion multiplier, for example, with any given roll of material.
That should really be untangled.