Hey Entropy, thanks for your review and comment! Somewhat ironically, there is client-side prediction but it's buggy, and so I think it actually makes things much worse! It only occurred to me later that since the player controls are force based, just allowing the client-side physics engine to move multiplayer agents works much better than the interpolation scheme I put in there (in the limit that the player executes no control command in a given frame, the client side physics should be 100% correct). I've already added quite a few features and improvements, so I'm looking forward to posting an updated version!
Thanks again!