I've personally not done any WIN 10 upgrades yet. In general, it's best to wait until issues have been patched before migrating. Ideally, until SP1 is released, but may be over a year away. Beyond the free upgrade period?
In my case, I know I will have some major issues upgrading my WIN 7 Pro PCs. One of which is my HP display monitors will not work, as their apparently is no drivers available. Granted, these are aging at this stage. But are nevertheless, greater than HD rez, with a high color gamunt reproduction, 70% left on CFL life, and among the brightest monitors still available. Not easily replaced without some $$. Though a 42" 4K monitor(w/display port) would be preference.
It should be fairly straightforward to revert back. But my practice is to always have a backup system image of WIN 7/8.1, should the revert create any issues.