This may turn out to be a great show.
Vandal Savage is a great villain.
Good to see Sara Black, this time as the white canary and as such not messing with laurel continuing to be the Black Canary on Arrow. Personally I like Sara better, Laurel sometimes seems a bit too whiny for my taste, but she's getting better.
The Atom never really fit the Arrow, so it would be good for him to be somewhere where he fits. Also - finally we will see his shrinking abilities.
Glad that Firestorm will get more screen time too. Also, I badly wanna see Killer Frost on The Flash.
Captain Cold and Heatwave - yay criminals/villains that will be on the side of the good guys, for a difference.
Hawkgirl - I do admit that I prefer the version of her that is a Thanagarian warrior, she's a welcome addition to the team.
And finally - Rip Hunter. Maaaaan, Arthur Darvill surely loves playing time travelling characters. It sorta feels like a Doctor Who flashback to hear and see him talking about time travelling. https://www.youtube.com/watch?v=vTypkdVrPFc