5 out of 5 rating for Curse of Strahd
I've been running this adventure for a few months now (one session per 2 weeks). It's not easy to prepare and run well, but it's well worth it for DM and players alike. Every session, I have lots of potential plot-twists and so on to think about, based on what's gone before, and what may lie ahead (including "what's Strahd up to now?") Three of us have been payers in the 3.5 version of this, while one played the 1e original three times; we all love this version for its new content and overall tone, as well as the classic Castle part which really is a big sandbox in and of itself.
While the potential for TPK abounds, my players navigated the "pre-amble" pretty easily (just a few minor NPC deaths). Once at the castle, one PC betrayed the rest (too many Vestiges taken on at the Amber Temple), and we had 2 PC deaths and the rest escaped on about 1 hp each - a vintage moment, leading to one returning as a Revenant, the other being Raised, and the turn-coat replaced by a player taking over van Richten.
My advice is simply to embrace the complexity and scope of the adventure as written, focus on the bits you and your players will enjoy the most (we skipped at least 3 locations), and be prepared to alter and/or enhance pieces based on your players and their PCs and their actions... there are so many good bits as written, but also so many more possibilities for putting the PC's into situations where it's not clear what to do, where the odds are stacked, and so on... basically, take the opportunity to make the players uncomfortable where you can (not all the time), and it can be very fun for all. Play on all the weird and dodgy NPC's, enjoy the role-play moments even against 'monsters' which the PC's may or may not kill (e.g. Baba Lysaga fought the PC's, but surrendered and made a bargain to save her life). In particular, be sure to make sure Strahd plays "cat and mouse" a bit once they hit the castle - the PC's are his new toys, be sure to make the most of it, before they finally get a chance to finish him.
It's an excellent expansion to the original, just be sure to read it well, then re-read the relevant sections at least once before each session. It's potential for excellence is really only limited by the DM and Players' willingness to embrace its style of play and make the most of it (i.e. not 'kick in the door and kill the bad guys').