Using a ProBook 4530s with the following GPUs:
AMD Radeon HD 7400M Series (EDIT: falsely recognized it seems, actual GPU is HD 6490M)
Intel(R) HD Graphics 3000
After installing 15.7, be it on Windows 8.1 or 10 the boot time starts to exceed 1 minute (using an SSD, usual boot time is 5-10 seconds), a black screen is displayed for about a minute with no particular drive activity before the lock screen appears. Waking up from sleep now also takes over half a minute. Another issue is how I can't seem to use the AMD GPU at all despite setting some applications to High Performance (global power play settings allow it).
On Windows 8.1 I was able to revert to an older version where I could manually select which GPU I wanted to use.
Trying the same thing on Windows 10 results in me not being able to open the Catalyst control center at all since it tells me there are no options to configure (although the painfully long boot times disappear). The 15.7.1 update didn't change a thing.
Some additional info on the fix:
Did the full cleanup as described in the manual and installed Leshcat’s Catalyst 15.7 WHQL UnifL (had to disable the creation of a restore point in options to make it work, made one manually just in case).
If anyone comes across this, this is the blog post with the download link: leshcatlabs.net forums • View topic - Release: Catalyst 15.7 WHQL UnifL
And this is the manual: Unified Leshcat Driver Manual
God forbid Windows 10 installs some kind of driver update now. I'm defering updates from now on and hiding all driver updates with the tool they released before I check for updates. PC boots normally and switchable graphics works.