Do not install El Capitan DP2 if your productivity depends on SmoothMouse. SM won’t work on it.
Apple has broken the API for pointer movement that SmoothMouse (as well as Wacom driver) relies on. This is also the reason why Wacom driver does not work anymore in El Capitan.
SmoothMouse had used the officially recommended API in the past, before version 1.0.5. Switching to a less supported API solved a lot of problems for our users.
We’re trying to reach the OS X dev team. Stay tuned.