These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: My Little Pony G3
Awesome Art: Several of the series' backgrounds were quite good, as were scenes with dark lighting.
Awesome Music: A couple specials have an electric guitar remix of the original My Little Pony theme.
"Wish You Were Here," which describes Rainbow Dash's vacation to Unicornia.
"Feeling Good", as Daffy Dazey gives Spike a bath.
All of the Runaway Rainbow songs were good.
"Shine On" from "Come Back, Lily Lightly"
"Nothing Says Christmas Like A Pair of Socks" from a Very Minty Christmas. A cute little number that shows off just how ditzy and adorably cute Minty is.
G3.5's "Somewhere Super New," as well as the main theme.
Bronies Hate G3: Pretty much every brony considers it to be the worst generation of MLP, due to the girly overtones, lack of conflict, and bland characters. The introduction of the Core 7 and the Newborn Cuties doesn't help much either.
Memetic Sex God: Star Catcher is this, especially around bronies who like G3.
The Scrappy: The general reaction to any G3.5 video is usually to the effect of "Kill it before it lays eggs!"
Moe Moe: Pick a pony, any pony and they'll be this.
So Bad, It's Good: Generation 3 is widely considered bad, no doubt about it. But it has a certain kitsch charm, complete with gloriously nonsensical logic ("We couldn't make you a regular-sized charm bracelet, because we kept making our charms too big. So we made you a giant sized one! And then we made you a regular-sized one!"), random dancing to electro-guitar versions of the theme song, and some genuinely amusing moments when it acknowledges how incredibly ditzy and incompetent its lead characters are.
Sweet Dreams Fuel: Yes, yes, yes it is. The specials have so much concentrated cute and optimism it's hard not to smile by the time you see the ending credits.
Uncanny Valley: Good lord, The Newborn Cuties. Are they human? Pony? Mutant? In any case, once you've laid eyes on them, you will have trouble sleeping at night.
We Hardly Knew Ye: Razzaroo and Kimono from A Charming Birthday. The most sane and levelheaded of the ponies, cute in their own way, and set up as members of Ponyville, they're never seen or mentioned after the special.
The Core Seven. The minority that like 3.5 maintain that they could have been much better characters if they'd given time to further the generation before being canned for G4.