For me, I like engine sounds, gun sounds, and a few other odds and ends. I don't like gear, wheel, or flap sounds to be screwed with. I've played aroudn with damage sounds -- this is one area I really don't like Mitsu's or Waffle's packs. Individually they're "okay" but when you actually fly with 'em they hurt more than help. I'm trying some mixed sounds that include defaults and some of (I think) Waffle's sounds. Not 100% happy, but it's a work in progress.
I rather like Sketch's gun sounds (for the most part), but they're too loud. If I can be arsed to lower the levels on all of them I might mix them into my current bastardized sound pack.