As with any non-stock camera app, I'm sure there is a bit of a hit to quality, since they can't access LG's closed-source camera, but honestly, I can't tell a huge quality difference myself. The Snap camera used in CM (as well as Bliss, which I'm currently running with Llama Sweet Kernel with some tweaks - I highly recommend this kernel so far for CM or Bliss, or just about any other AOSP-ish ROM) has taken some big steps forward since CM was first available for the G4. (Full disclosure, some people have had issues with the flash going at the wrong time, causing over/underexposed pics, but I haven't seen it on mine. Others have also reported a bit of a hit to video (some lagginess) but I haven't taken any video yet to confirm or deny.)