I studied the adventure fairly extensively in preparation for running it, though I haven't gotten around to doing so. I also played through about half of it. My first comment is that it's a pretty interconnected adventure with a quite strong plot thread running through, but it's hard to realize this in how it's written. The whole book is laid out kind of like a computer game, by area instead of by story like many other adventures are, so if you want to get an idea of the story beats the players are mostly expected to follow, though they can strike off and explore, you're going to have to hunt through the book.
A good example of this contained within a single area is in Strahd's castle: Several events throughout the book lead to the characters getting a formal invitation to dine with the Prince. When they follow the invitation, Strahd's chamberlain awaits them in the entrance hall and leads them to the dining room, where they find Strahd playing the organ, he talks with them briefly, then mocks them and disappears. But this is not presented as one event, rather the section on the entrance hall simply reads "The chamberlain leads the characters to the dining hall area" and then the dining hall section says "when the characters first enter, they find Strahd playing the organ, etcetera".
Basically all the plot lines are presented like this, often across multiple parts of the map, and there are a fair number of them. This isn't bad as such - the point is to enable a sandbox approach, and the module does a decent job of bypassing the inherent problems of sandbox play - but I definitely recommend reading through carefully and making notes on interconnected events so you can plan for them and don't miss them.
As another general note, it is important to keep in mind the kind of players you have and how they will react to dangerous situations. Curse of Strahd cavalierly lets you walk into encounters you really can't handle, so have a plan for signaling to players that an area is very dangerous, or that an encounter is out of your players' league, and a way of handling retreat outside of the combat system. For example, if you want to start at first level, the final encounter of Death House is a shambling mount, a CR 5 monster that four or five level 2 characters really aren't going to kill on their own unless they do something like slow it down and then bring the house down on it (as my group did). Make sure the players realize a heads-on confrontation is a bad idea as early as possible, and that they're not necessarily shackled to the combat system.
Lastly, two specific encounters that left an impression in actual play, one good and one bad: First, at the vineyard, there are three druids and hordes upon hordes (double-digit numbers) of blights. When I read this on paper, it seemed like the kind of ill-conceived fight that doesn't actually work well in a game, but when we played it out, it actually ended up being tense and well-paced. The best way to fight this is to not stand your ground, keep moving, and take out the druids one by one - they all start out alone, so they're actually easy to kill if you move quickly and don't give them time to regroup and the players feel like a badass fantasy SWAT team. Just don't actually take the blights' 30-50 turns individually.
Second, the revenants at Argynvostholt. There are a few ways to earn their hostility and be attacked by them within the fort. The problem here isn't so much the danger - you'll probably be level 4 or 5 by the time you poke your head in there - as their durability. Once you leave the fort, you have an order of implacable enemies, and that's fine, but within the fort, you get attacked by large numbers of monsters with high hit points, high AC, regeneration, and not very exciting combat tactics, so that fighting your way out is a huge, boring slog. In this case, they're not individually so threatening that it's a clear signal the PCs should cut and run, so they're like as not to commit to fighting the revenants (and possibly be overwhelmed by attrition anyway).
