Do not enable USING_CEP' in CSD's options file as this will cause fatal issues with the game. This setting will (according to Gazebo, author of CSD) be removed from future versions of CSD.
Furthermore I recommend against enabling the options "CSD_POLICIES", "CSD_BONUSES" and "ANCIENT_WONDERS" in CSD's options file as this will most likely cause unintended behaviour from e.g. the affected policies. However it shouldn't cause fatal issues.
You may want to clarify that the policies, bonuses and wonders are all enabled by default, and that players will need to disable them for full CEP compatibility.
I still think we should work on policy compatibility at some point, but I think I'm 'big-project'd' out right now.

Edit: also, in response to the discussion about CSD's policies being necessary or not, they aren't. I buff patronage to make it competitive with the other medieval policy trees, however CEP's patronage tree is also better than vanilla's so that's a wash. The only policy CEP would need to modify with CSD enabled is to change the boost-to-gold-gifting policy (can't remember which that is). A simple fix would be to disable that policy's gold gift bonus, then add in a +25% to Great Diplomat spawning (or, to be compatible with the non-dll version of CSD, a boost to diplomatic unit production or something). If you fix that policy, all should be compatible. I strongly encourage players to turn off gold-gifting. Is redundant with CSD otherwise.
Some of the elements of CSD (like the belief and sweden fix) aren't even necessary anymore, because diplomatic units aren't 'special' anymore (and therefore can't be abused for great person-related beliefs like Reliquaries). I plan on removing those (or at least disabling them) in v17. v16 was all about the DLL.
G