On the iPhone, when a set of views have different colored and textured navigation bars, what is the best way to animate in the new view when the user taps on a tabbar icon? Should the new fade in while the old fades out, should it come from the side or should it just replace the old view without any kind of animation?
Judging purely on my experience (of the apps I've used), there is rarely animation of any sort when tapping a tab bar button. I'd go for no animation, personally, based on convention.
Swiping is more suited to going back/forward and fading is rare - almost animation for animation's sake, rather than a constructive addition to the UI.