I enjoyed that everyone had fun with all of the crossover shenanigans (and it was cool to learn that this Earth has its own Central City...how foreign would it seem to Barry without those familiar faces?), but it was frustratingly easy to tell there was once a scripted version of this episode without Barry in it.
I dunno about that, seeing as how the producers pretty clearly wanted this to happen from the start, and given how smoothly the arrival of another, supportive superhero and romantic rival for James fits into the developing arc. Not to mention the symmetry of having a supervillain team-up and a superhero team-up in the same episode. Not to mention how The Flash worked in a glimpse of Supergirl seven weeks ago, demonstrating that this was hardly a last-minute addition. But it's possible that they deliberately broke this story so that it could work with or without the Flash, just in case the negotiations and logistics of the crossover didn't work out. The Flash-less version would've been a Plan B in that case, rather than their original intention.