The annoying thing is that it didn't seem to fit in continuity-wise with where they left off on Flash last week. Last week they just discovered that Zoom is Jay (or a version of Jay), and I expect that this weeks Flash will pick up from that exact point. But for some reason Barry just randomly popped up on "Earth-CBS" wearing a version of Reverse Flash's tachyon recharger. They never explained how he got it. (If Mercury Labs gives it to him later on this season, they we know they were aired in the wrong order.)
Last season, whenever they did a crossover between Flash and Arrow they lined up the continuity between the two shows perfectly. I guess its much harder since they're making arrangements between different networks.