I think it has to be treated carefully, although it can have a place. I've never dealt with a program that does a reward for EVERY new skill for everyone, but I don't necessarily have a huge problem with it (see below for my initial reservations). For a garden variety, just not getting it fast enough roadblock, I think for both coaches and parents, moving to bribery should not be the thing that comes up as a solution, per se. Team kids most likely went through levels 1-3 and got everything relatively fast, but that won't always hold true at the team levels and due to natural strengths and weakness there are going to be places they struggle. I think that an outside bribe can make kids work harder, but I've also observed it to reinforce some things in the young athlete's mind that I would consider negatives, and it doesn't handle it as matter of factly as I like.
On the other hand rewards are nice so they know their hard work isn't going unnoticed. If I see someone working hard, I make a point of saying it loud enough for everyone to hear. If someone is consistently trying hard on their stretching and conditioning, they can lead. If someone is listening well and cooperating, they can demonstrate. I prefer rewards that are related to effort and team citizenship rather than related to gymnastics ability. Some girls will still breeze through level 4, 5, 6 quite easily and with less effort than someone else. This is what would concern me with a blanket "reward for every new skill" policy, because it doesn't mean they are trying their best and coming with a good attitude every day, and it doesn't mean a girl who isn't getting the skills isn't trying her best and has a bad attitude. It might get discouraging for the latter set to watch someone who cheats through conditioning and misses turns to constantly get attention for new skills...and there are girls who do those things that get skills at the lower levels.
I think that has the potential to create a culture where rewards come from just doing something in the short term and then you move on to get the next reward. I would rather that girls appreciate that, for example, conditioning to their limit with good form every day will make skills look better and easy down the line. That is hard with little kids 6-10 and requires continuous feedback. I think for a lot of coaches laziness is our worst enemy and it's easy for us as well to resort to things that we observe as getting short term results. I had a coach at one point for a short period that was very "carrot stick" in that way (not with actual rewards, we were mostly teenage L9-10s at the time) and he was all right and could get people to make quick improvements by throwing something short term, but ultimately the situation literally just fell apart and his attitude and the constant threats and favoritism played a major role in it. That taught me a lot about bitter people who constantly seek credit and try to get credit without putting any real work or heart in.
Anyway, heck I was in groups with girls in L6 whose parents were bribing them just to go to practice, needless to say they were never optionals. I think most people understand where the reasonable lines are. If you're crossing them, you have to step back...if it's still working all right I don't think you necessarily need to analyze too far or worry that rewarding your daughter for a skill once is going to set her down the dark path of instant gratification. At the same time I think we need to realize that a lot of the more troubling aspects of our culture and some things we want our children to reject are related to a desire for instant gratification.
It's one thing to say "I noticed you have been working really hard and I am proud of you. I want to take you for ice cream/shopping for a new shirt on Saturday" and another to say "if you beat Sally Smith tomorrow you can get a cell phone." I got straight As in school and my dad used to try to give me money for it. My parents still try to give me money for things like that. I think it's the most ridiculous thing. There is NO way that at the beginning of each grading period I was thinking, hmm, I'll get money if I get straight As so I think I'm going to do that. It had nothing to do with that and even if it did there's no way I could have sustained 7 IB classes, volunteer work, and gymnastics my last two years of high school solely based on rewards. I did those things for a lot of reasons, some of them good, some of them bordering on a little destructive if I'm honest, but it wasn't for money.
) My girls, like all our girls, really want to place, but sometimes their best is just not good enough, so I figure a new leo will heal the pain. But, it may be counter productive too, who knows. 
