Well, this is frustrating. Kurt Busiek usually pulls off really good opening sequences--the first issue of Thunderbolts (his previous extended collaboration with Mark Bagley) was a deceptively straightforward-looking story with a killer revelation/cliffhanger at the end, and after he noted that JLA: Syndicate Rules would provide some backstory for Trinity, I read it and enjoyed the opening chapter's everything-bad-is-good mayhem a lot. And I know (from having interviewed him for PW Comics Week about it) that Trinity is meant to be pretty formally ambitious; I really like his idea that it's constructed as "a hybrid between a traditional comic book and a classic continuity Sunday page." So it's strange to see this 1000-plus-page story begin with an issue this bland and groggy. What we get is three pages of cosmic mysteriousness (cf. the first two pages of 52 #1 and the first page of DC Universe 0), followed by an extended scene of Superman, Batman and Wonder Woman's civilian identities eating breakfast and chatting about having had weird dreams lately. The obligatory action sequence is the Flash and his kids fighting Clayface, because... an action sequence is obligatory, and no other good reason, as far as I can tell. At the end, something blows up near Superman. More intriguing things than that have happened to me on the way to the comics shop. This reads like a character-driven story, and Busiek's got a convincing sense of all three principals' voices (although I can't quite hear Bruce Wayne saying "Glad you could make it, buddy!")--but the characters don't actually drive the story anywhere in particular. Bagley's art is perfectly solid; his storytelling instincts are as good as ever, although he really hasn't got much of a handle on Batman or Diana Prince yet. As Brian noted, the lead feature doesn't stumble, but it plods and dawdles where it needs to fly.
The backup, though, is a pretty severe mess. It pretty much spells out the fact that it's Establishing a Premise: our bad guys for the series are going to be Morgaine le Fay (I don't know if I can take a whole year of dialogue like "By Accolon's blood! You have some small wisdom, cur--but you court infinite pain by insulting the witch-queen of Camelot"), Despero, and a new character called Enigma who talks like a cross between Spider-Man and Mojo Jojo. There's a new character called Konvikt whose dialogue seems to have been ported over from a Bill Mantlo-era issue of The Incredible Hulk. And the Big Three represent the major arcana of Justice, the Devil and Strength, fancy that. The one intriguing page is a variation on Geoff Johns' "coming attractions" trick: a flash of a possible future involving Green Arrow, Ragman (and... Ragboy?) and a cig-smoking Lois Lane. Mostly, though, there's so much bulky expository dialogue it hurts.
I can't help but compare this to the first issue of 52: a densely packed tour of a world of wonders that reintroduced half a dozen characters, established a couple of big mysteries, and ended on a relatively low-key moment--Charlie turning the Question-signal on Montoya and asking "are you ready?"--that was still an omigod-what-happens-next hook. The beginning of Trinity, unfortunately, is pretty much Eh. I've got enough faith based on Busiek and Bagley's history, individually and together--and I miss having a book I looked forward to every week enough--that I'm going to keep reading for a few more weeks to see if it picks up, but this isn't an auspicious beginning.
BONUS QUESTION ABOUT SECRET INVASION #3 THAT I'D APPRECIATE IF SOMEBODY COULD CLARIFY: I may have missed a crucial tie-in or something, but the last time we saw the Helicarrier, hadn't it gone into total systems failure over Manhattan? How did it manage to land in the Bermuda Triangle?