I didn't realize how much I didn't like the BREAK cards until I just went off on them one day while talking to a friend. Both from a competitive standpoint and from a collector's standpoint, I don't care for them; they're pointless. (It's possible they'll become better in the future, but as of right now, there are no redeeming qualities.) Incoming rant:
I started playing the TCG at the end of the DPPt era, when the Arceus set had just come out, and Lv.X's were awesome! In my opinion, when comparing BREAK's to Lv.X's, I think BREAK's are just a little bit better, mechanic-wise, since your Pokemon doesn't have to be the Active Pokemon in order to BREAK evolve. But when comparing the two in the formats they were in, Lv.X's worked because they were the big, strong cards in that format. BREAK's are in a format with big Basic EX's, making them obsolete. Why on earth would I want to spend a minimum of three turns setting up a BREAK Pokemon that is not as good or is on par with a sub-par EX? There's no way Pokemon doesn't know that the general consensus of Stage 2's is that they're not very viable when compared to EX's. (Which is a shame since there are many Stage 2's with either strong or interesting attacks or Abilities--or both!) If they really wanted to BREAK evolution, I think they should have made some mechanic to speed up evolution while possibly also giving an increase in HP or damage or possibly both, just to be on par with EX's. (But who knows. Maybe that would spiral out of control and create even more of a power creep.)
And from a collector's standpoint, this might just be me, but it's frustrating to see even MORE ultra rares in sets. BREAKthrough is going to have 8 EX's + 10 FA's + 2 secret rare FA's, which is 20 ultra rares; that's plenty. Oh, but wait. NOW there's 6 BREAK cards! Let's bump the ultra rare count up to 26! What's the typical ultra rare count for a booster box again? 4 to 8? Sure feels good knowing that after spending around $100, I'll just be putting a dent in completing this set. And on top of that, the fact that the BREAK cards are being panned as not playable, that will probably mean they'll be worth less. (Thundurus EX from Roaring Skies, for example? $3.) So not only is the number of ultra rares increasing, but so are the chances of getting an ultra rare that's not playable. I will say, though, if they treat the BREAK cards like they did with Prime cards (making them take place of the reverse instead of the rare in a pack and also having 4 to 6 of them in a booster box on top of still having 4 to 6 other ultra rares), I would be completely fine with them. But I don't see that happening. They'll probably just take the place of the rare, like any other ultra rare.
As for aesthetics, I get why they made them sideways. It's just so you can still see the previous card's attacks, Abilities, Weakness, Resistance, and Retreat Cost. It looks kind of silly, but it's fine. As for the holo effect, I've always found that sort of design/pattern cheap-looking. It's like something you'd find on a sticker from one of those sticker vending machines. (Maybe it'll look better in person, but I don't think I'll be sold on it.) And the golden CG Pokemon themselves... I've never found CG appealing when compared to more traditional artwork. With traditional artwork, you have so many visually appealing options. The artist's style, the colors used, the detail--there's so much that can make a card's artwork visually pleasing! With CG, it's just that Pokemon. In 3D. With a 3D background. It all mostly looks the same, aside from maybe the effects added. I can absolutely appreciate the effort put into 3D models! It's just not my cup of tea. And making the Pokemon golden is pointless, in my opinion. Is it just to try to make them look more important than they really are?
TL;DR: Competitively, BREAK's are pointless when EX's also exist. They're increasing the amount of ultra rares in a set while also increasing the likeliness of pulling an ultra rare that isn't playable and is, therefore, basically almost worthless. And the holo pattern looks cheap and CG isn't visually appealing to me; golden Pokemon or not.