I hate most that I have to compile my modules into ogg files for delivering them with wintermute -- for modules are much smaller and sound better when played back natively ... second pro for modules: music fadings can be done more subtle, just imagine unreal 1. Just change the playback order, when the scene changes, and the module will play different parts of the same tune.

Second most hated fact is the current default language support only works through packages. This idea is great for deploying native products for every country, and for downloadable language packs, so I won't encourage you to drop it -- it works as intendet. BUT it would be very nice to have an ingame language switching support as well, for games which should be distributed in one version for different countries. Szenarios include (but are not limited to) advertisement games deployed at fairs, where you just cannot decide which language suits your current customer best. We found a workaround for this in The White Chamber, and a native support for different languages in one distribution is not very hard to do on side of the engine.