Admittedly, the changes to Ancient Power and the like aren't exactly what most players were hoping for. They still provide a 10% chance to turn the user into an unstoppable force which can more or less win the game on its own. However, with reduced incentive to run these moves in the first place (notably for Giratina in Ultra League), and reduced benefit to just spamming them, the frustrating from going up against a boosted Pokémon will come up less often.

As far as meta implications go, it'll be hard to tell just yet. With Giratina likely shifting to Shadow Sneak, it has less counterplay against things like Togekiss and Articuno which it previously threatened pretty heavily with Ancient Power. This may make them somewhat more prevalent. Giratina also gains a lot of power against Registeel. This then alters the triangle to make "Giratina <- Giratina Counters <- Registeel <- Giratina" more defined. This change is live now, so be prepared to keep an eye on the meta shakeups as Ultra League GBL continues.

Cherrim is now potentially a very strong pick in Voyager Cup. Previously, Meganium seemed to be coming out as one of the most popular corebreakers to beat Registeel/Azumarill. However, being Gen 2, and if you're already running Azumarill, it took up your Flex slot. Cherrim, on the other hand, takes up Gen 4 instead, freeing up your Flex for something else.

Master League is an interesting one, and the degree to which it's affected is heavily reliant on how hard Giratina-Origin is hurt by the nerf. Previously an incredibly strong Pokémon, and definitely a meta-defining one, it remains to be seen how much weaker it actually becomes. Togekiss, primarily just there for using Charm, is weaker after the Ancient Power nerf, but likely not meaningfully so.

It's definitely exciting to see how the meta is going to shape up over the coming weeks. It's always appreciated when Niantic shakes things up, especially when they make weaker moves more usable.