I like tipping. I like it because it's not tied in with any of the politics of voting, it feels like a much more straightforward demonstration of appreciation. Sometimes, I vote and tip (I know, what am I like)? I like the little gift icon and you can just tip there and then and tip a comment, too. You're right about the long-tail rewarding of good content, I think it can also increase and reward engagement.
I'm a bit confused about cross-posting ... peakd have introduced a fix where rewards are declined on a cross post and the votes go through to the original post (that's good and less confusing) ... but I thought one of the huge potentials of cross-posting is that content could be re-discovered time and again by new people coming across it, and the author continued to get rewarded each time it was re-discovered. I'm not sure that will happen now?
To be honest, I've never understood the cross-posting thing. I didn't take time to look into it. I did notice that the community you cross post into might be able to take a percentage of the payout too.