So I just watched the most recent MLP episode and I have to share my thoughts on it.
Some quick background, I really usually hate Fluttershy episodes. I think they try too hard in most of them either do too much fanservice or force really false development on her that doesn't make sense within her character. And honestly, when I started watching Filli Vanilli that's what I expected. I enjoyed Dragonshy and Keep Calm and Flutter On but the former is the exception to my 'false development' feelings and the latter had Discord, so how could I not enjoy it? I didn't hate Bats! either, but I didn't love it and thought the fanservice was a little questionable. HOWEVER...
Filli Vanilli is the best Fluttershy episode EVER, even better than Dragonshy, and definitely the best since Season 1.
Whereas the Fluttershy eps in S2 were forced and unnatural feeling (Fluttershy gets assertive for no reason at all) Filli Vanilli was actually really really REALLY well done in terms of Fluttershy's character. And whereas Keep Calm and Flutter On was good, it still lacked an element of development. FV involved Fluttershy actually working to overcome her fear of performing, a fear that as a "drama kid" I've never experienced, but am still intimately familiar with through my friends and comrades in performance. It didn't have her suddenly overcome her fear the way Putting Your Hoof Down and Hurricane Fluttershy (still my least favorite episode) did, without any real work to get there, but actually had her experience performance through being the voice behind the face, and an accident that forced her into the spotlight. It also got her to the point of being comfortable singing in front of her friends but not in front of outsiders, something that fits well into her introverted personality. I was feeling "meh" as far as looking forward to this episode but for a Fluttershy episode it blew me out of the water. Fluttershy is still my least favorite of the mane 6, but this episode, although it had "Flutterguy" fan service, it was like the other fan service in S4, well played.
There were also some really nice moments between Fluttershy and Rarity, something we haven't seen in a while, and we got to see Fluttershy interacting with Big Macintosh, and even a moment of hilarious Big Mac/Applejack brother/sister brainwave communication. My only complaint is Pinkie Pie being a little insensitive, but that still fits within Pinkie's character, and the fact that she admits to being good at being ridiculous made me laugh. Rarity was further enforced as my favorite of the mane six through the caring way she handled Fluttershy throughout, only agreeing to perform when Fluttershy insisted, knowing all along that Fluttershy wanted to sing, and not pushing her when she didn't want to perform in front of others. This episode really truly showed all the characters (except Pinkie) at their best, something that doesn't happen much. It's honestly up there with Rainbow Falls and Rarity Takes Manehatten for my favorite episodes so far this season, which is really truly an accomplishment since I usually HATE Fluttershy episodes.