Pretty great trade for the Mets. Yes it sucks that a elite pitcher will be traded, but the Mets likely won't compete the next year and two and the Mets have a strong rotation and badly need young offensive help and they got the top catching prospect and easily one of the top prospects in the game and also got a top flight pitching prospect and dumped two bad catchers. Dickey will be missed and the Mets are worse off in the short term, but with the return they got for Beltran and Dickey the last few years the Mets look to be headed in the right direction even though they'll take some lumps along the way. That said short term the Jays are gonna be really good as the Yankees and Red Sox are weakened and the Jays really have a three year window to win with their core. If they don't make the playoffs during that time this trade will not be all that good for them and will cost AA his job.
If you truly believe that McGwire was big his entire career, please do a Google image search for 1987 Donruss McGwire, or 1987 Topps McGwire, and tell me he stayed anywhere close to that size, both in body and face.