My biggest concern for Doomsday Clock is that all this buildup will have been like the buildup we got in the Countdown weekly series to Final Crisis. Countdown (and Death of the New Gods) ultimately had nothing to do with Final Crisis at all, which ultimately made Countdown even worse in retrospect.
First, as an aside, I don't think Tim Drake was abducted by Manhattan just MISTER OZ but I haven't been reading DC books that aren't Tom King, METAL or Justice League related the last few months so anything Detective or Supes is more for Tasty to reply to.
Countdown was never intended to lead to Final Crisis. It was supposed to be "52 done right" and then at the end it became Countdown into Final Crisis even though they didn't actually bother to check with Morrison, Johns or Rucka about what they were writing for Final Crisis. (Neither did the Death of the New Gods author.)
The one thing they did want to establish were the different Monitors and how they each had their own universe. Which they had already established in 52 I think. In the end, Morrison and Johns wrote DC Universe #0 to establish the stuff for Final Crisis and Blackest Night that they needed established. And Morrison wrote extra panels and part of Superman Beyond rehashes the Multiverse, the Bleed, the Monitors, etc. through random exposition because they didn't want how Countdown did it.
You could argue Morrison and Johns wound up giving more canon status to Countdown than it had earned when they established the Multiverse having been progressively destroyed AND Superman-Prime in the tie-in books. Morrison even suggested that had he been able to know what happened in Death of the New Gods he would have changed Final Crisis to better incorporate it, even though those events were so stupid that Morrison's killer (effectively old age) was much better. He did change the virus name to match the one in Countdown even though they did different things in the two books. Rucka completely ignored Countdown for Revelations because he was straight-up finishing his story from 52 under the premise of Final Crisis being the day evil won.
Doomsday Clock shouldn't have any of this because it's still a standalone book with a set number of issues. The Button was to erase Flashpoint which wasn't supposed to reboot the DC Universe originally, but be more like Age of Apocalypse, where for a while the universe was different then it came back as before with minor changes that hung over. We just took a five year plus detour to do that. That's why the other appearances of Manhattan have been to do the same things to the New 52, like how he erased Pandora, who was the one who originally "combined the three universes" in the wake of Flashpoint and created the New 52.
Flashpoint never happened as we knew it, so the New 52 never happened as we knew it, so Convergence probably didn't happen as anything other than a crazy Braniac scheme thing instead of literally universe altering. No matter what, I'm just going to pretend Convergence never happened other than as a wacky adventure that killed half the main cast of Earth 2 before sending them to their new planet for the rest of that slowly degrading story.
