The main reservation I have about Infinity War
Marvel Studios hasn't bothered to introduce any kind of cosmic authority whatsoever into their verse besides maybe Odin, but they want to make a two-part movie about the Infinity Gauntlet. (Obviously Galactus and the Silver Surfer are outside of their permission)
All of their movies besides GOTG have been too focused on Earth (yes, even the Thor movies). I'm seriously hoping Doctor Strange expands the verse so that we're properly prepared for IW.
Thanos' scene in AoU was cool, but it was completely hamfisted in. Thanos himself had no real connection to the plot besides the fact that he gave Loki the Scepter in A1, so him going "Fine, I'll do it myself" at the end of this movie made no sense whatsoever. Whedon should have incorporated Thanos into the plot more, given him a role like the one he had in GOTG.
Ragnarok, Civil War, and Doctor Strange all need to be preludes to Infinity War for this to succeed