The FMOD sound system was well worth the change, it added quite a bit of depth in 3D sound.
Problem is it has a bit of a learning curve.
Like any old sound pack, getting flawless loops in engine sounds can be challenging.
Anyone can use it and create new sound packs.
Chalenger's approach was using many actual live recordings of the AC he recorded himself. He was on the verge of polishing them up when he passed. Some of the actual AC either just don't run or exist anymore. So getting those recordings is fubar.
Frankly, I find very little problems with the defaults.