I've used CK with Biotera Gel, Deva UDG, and CJ Curl Queen, all with very good results. With Biotera and UDG, I've tried both mixing and layering (both worked well). I haven't had the Curl Queen long enough to try mixing it with CK, but that will be one of my next experiments.

Modified CG since 11/5/11
CLEANSE: CJ Daily Fix, DevaCare No-Poo, CHS Treatment Shampoo
RO: SS Caitlin's Conditioner, CJ Beauticurls Strengthening
LI: SS Repairing Protein Treatment, CHS Silk Leave-In
STYLE: Re:Coil, Curl Keeper, Deva Ultra Defining Gel, Curls Rock Amplifier,Sweet Curls Elixirs Okra Gel and Hard Hold Gel, SS Curl Enhancing Jelly and Firm Hold Gel