I'm really enjoying what I've read so far, as the adventure involves a lot of side plots and factional involvement and conflict. Given player choices should they align with one or more factions, the adventure could go in all sorts of directions, even before choosing the seasonal villain (and, given the set-up, Xanathar and Manshoon are likely going to be involved in the plot even if they aren't the "chosen villain").
One further thing - the summer choice, the Cassalantars, is a really dark, no-win situation. Should the players succeed or fail, innocents are going to suffer, quite horribly, unless the players do something amazingly clever and extremely unlikely to somehow peacefully resolve the Cassalantars' situation...