We've seen a Moon Druid in action in a level 1-7 campaign. Simple responses: Yes, it's a common reaction. Yes, the party's primary fighter felt a bit miffed (at first). Yes, the beast forms become less "wow" as players gain levels. And as a final yes, the player ended up loving the druid, and the other players embraced doing what their characters do best. I have come to believe that the primary complaint about Moon Druids isn't really about the mechanics but rather players who attempt to "do it all" and take away the spotlight from others. That's your danger zone in any group, druid or not. That's why the party's fighter felt a bit miffed when the Bear was outpacing him. It diminished why he was at the table playing that type of character. But, I've got a great group, and one of our core tenets is making the game more enjoyable by sharing and encouraging others to do what they do.
So as to your core question, experiences? We all should keep in mind that D&D isn't, and shouldn't be, balanced by class. There's something unique about playing each class, as you get powers and milestones at various levels to contribute in a special way. We saw:
- the animal forms become less powerful each level past 2. It's that level 2 bear form that makes everyone go "woah."
- the beast forms drop pretty quickly by 5th level, a round or two. They're super easy to hit. Your humanoid form gets squishy by 3rd level and on, and your AC will generally always be poor
- Unless your battles are all melee, the animal forms aren't always useful and the "woah" factor lessens. Is there a sniper on the 2nd floor? A wizard across a river? Elevated levels in a cavern?
- You can't talk in animal form. That's great to scout, but you've got to burn your shape shift to talk. So, you become very short rest dependent.
- Concentration spells to augment combat are nice, but in a heat-of-the-moment battle, it's not always convenient to spend a round "getting ready" while other players (and enemies) are dealing damage, controlling the battlefield, and incapacitating
- it's a jack-of-all-trades character in some ways. Which is great! After a PC death, our druid took over as the "tank" (hate that term, but the guy who charges in screaming to get attention away from the others). He wasn't as good as a Fighter-class would've been, but the others supported him and made it work. I suspect had a pure spellcaster been useful, the druid character could've fit that role well-enough
- 6th level was a much needed "bump" in power with new forms.
- No one else gets to shapeshift or cast some of the spells you can. Makes your character unique
- It's fun to play.
So, moral of the story, we all shrugged off our "woah" moment at 2nd level and enjoyed the game, keeping in mind the game is better when we prop others up rather than try to diminish them by "doing it all." The druid has its pros and cons, and it's the blend of both, as it is with every class, that makes playing each of them a unique experience.