Let me save you a LOT of frustration down the line. Stop playing the Season 4 expeditions. Simply put, they are terrible. There's one, maaaaybe two that are worth it. The rest are so bad and disjointed your players will end up more frustrated than anything else.
While I wouldn't go that far, I have to agree to some extent. For my group, it is by far the most fractious season by a wide margin.
On the one hand, the whole season is just dripping with flavor and atmosphere. That's a good thing, and it's been the number one aspect that our group has liked. As to the quality of the mods, I've found those to be about on-par with most of the ones in previous seasons -- a few good, a few bad, most middling, and the majority fraught with varying degrees of just shoddy editing.
That said, however, the (admittedly experimental) approach of the Ravenloft season has brought with it a host of other, newer issues.
The first being the 'continuous storyline' aspect, wherein the modules are all telling a single, long story arc across the length of the season. While a fine idea in theory, that sort of aspect lends itself poorly to a compartmentalized release schedule like this. Many times my players were continuously surprised by amazing "sudden" appearances in the area -- such as the Hospice, or even the Giant Foreboding Ruined Manorhouse overlooking the village from the top of the cliffside -- because the elements are only mentioned in the modules that they appear in specifically. Even the population is getting bigger as time goes one, it seems. The first couple of mods seem to imply there's just a handful of villagers living there, but we're up to practically a thriving town, it feels like, near the end. These are all things that are easily understood to 'be there, but not important at the moment' if something like this were, say, a hardback adventure, with all the pertinent info at the end in some appendix. Unfortunately, with the shifting info being doled at per module on a need-to-know basis, it becomes very disjointing for players and characters alike.
The lack of 'portability' in this Season 4, however, is by far the least-liked aspect, by both myself and our players, and has been directly responsible for a rather dramatic reduction in the number of players we get at the gamestore anymore. By being 'locked' into the season's mods by virtue of playing them, we've had very few individuals who want to 'hop in' to a game, like we had in seasons past -- because they have no idea if they'd be able to make the adventure that allows them to escape. Recent revisions to the campaign rules allowing for other possible escape routes are a nice attempt to rectify that, but for several of our players, it's too little too late. Our numbers have dwindled by half over the course of Season 4 explicitly due to this fact, and we're hoping that with the arrival of Season 5, we'll be able to get some of those players back. Mind you, we're just a small gamestore running AL stuff when we can here, so we're often struggling to get a legal table some weekends anymore. We don't have the luxury of having so many players that we can often re-run mods a second time anymore (what with everyone's oddball schedules, etc.). In seasons past, we could often run a mod a second time with new players if we had them, but with the 'being locked' aspect of Season 4, people aren't even willing to try it, for fear of having their characters lost with no likelihood of the 'escape mods' showing up. Again, some other escape routes have been added, but not in time to rescue the interest of some of our players (and for those that tout the accessibility of online play to take care of any gaps, that's a poor option for many players, for a variety of reasons).
The greatest irony, I fear, is that all of these potential issues had even been brought up on the forums well before Season 4 had been announced, as several of us had been talking about the possibility of seeing WotC put out a 5th-edition Ravenlift revamp.
Regardless, while I feel Season 4 was a noble experiment, I would not, personally, call it a successful one by any means. Going forward, I hope to see some aspects -- such as non-portability -- buried in an unmarked grave somewhere, and at the same time hope to see some of the more successful aspect being delivered in a more player-friendly method in Seasons to come.