This volume actually features a milestone or two. For one, Barry finally marries longtime fiancee Iris. For another, he tells her he's the Flash...about a year later. Sort of. There's also a race with Superman that ends in a draw, or at least in such a way that the readers can conclude on their own who won, and a story where Barry visits the real world and meets DC editor Julie Schwartz.
So, that out of the way, here are a few downsides:
1. Mopee. One of the most hated Flash stories of its era, apparently, has a bumbling cosmic angel/wizard guy altering Flash's origin (sort of) but in a way that obviously would be ignored from then on.
2. A two-part Flash-in-Japan story, which could have been nice had not every Japanese character been both written and drawn in the worst stereotypical way possible. Buck teeth, glasses, and bad English all the way around. And that's the only multi-part story in the volume.
3. Attempts by writers to make Barry hip by having him use slang from the era (late 60s). Sorry, Barry looks like a square. A bow tie and hat combo doesn't lend itself to youthful slang.
4. Carmine Infantino left the book at some point to be replaced by Ross Andru. Andru is a fine artist in his own right, but he doesn't have the same sort of dynamic style that Infantino's art gave the character, and it doesn't look as nice.
Beyond that, if you like Silver Age Flash, you'll like this.