I don't have any of these, but I think it'd be cooler if they would stick with the classic smile, just with more additional features available like eyelashes, blushing, eye patches, facial hair, scars, face paint, and such. I mean... that pretty much covers mostly any additional features I guess.
I think that all of these function well, considering any "bad" figures look bad enough with their outfits and eyebrows (but not the wretched painted-on faces of some Dragon Land people...). Some of the other faces on the series 2 figures seem weird, and the head turning thing seems annoying to me.