I played in this under 1e long before I ever ran it as a DM. The module had just been released and my DM had played in it himself and suffered a TPK at the hands of Strahd. So, naturally, he wanted to try it out on me. It hurt.
We were completely duped by the false reflection of Strahd and decided that he wasn't really a vampire and we were probably going to be OK. We wandered about the place getting progressively creeped out, until we finally ran across his diary. Just reading that handout in a candlelit gaming room was a horrifying experience. All ideas of getting out OK fled. And then Strahd turned up and the running and screaming started.
Our Stupid NPC Sorceress was first to bite the dust (as per usual we sacrificed her to give us the chance to flee) and we began a panicked flight to reach the highest point in the castle possible. Our fortune telling had told us that we would find help there and so most of the adventure became a terrifying hit-and-run battle upwards through the spires of Castle Ravenloft. The goodie in the tower turned out to be the Sun Sword, which my fighter's assassin girlfriend took possession of. Strahd didn't seem able to enter the tower, so we rested up, girded our loins and went leech-hunting.
Of course, the DM had been concealing Strahd's magical powers from us up to now, and we had just assumed we were fighting a buffed-up vampire. I was particularly smug because of the fact that my fighter had one of those wonderful 1e negative ACs (it was -8 or something silly like that) and I figured there was no way in hell that Strahd was ever going to land a hit on me and drain my lovely levels away. Umm, yeah, right.
One polymorph other spell later and my ubercool fighter became an ubercool small white chicken. Whom Strahd promptly drained down to level 6 (from level 10) in a couple of rounds flat. I panicked. I ran. I squawked. I flapped my wings and did that stupid "look at me I can't fly for




" thing that chickens do. Soon after that we ran into the iron golems.
During the battle with the golems (I had been de-chickened by this point) another player from the TPK game arrived to spectate. Being the unsporting swine that he was, he stood behind the DM and mimed that we should look for the hidden gem. It was all that saved us. We nailed Strahd a little later. So, yeah, I only made it through Castle Ravenloft by being a dirty little cheating ratbastard.
Like a few other posters, the adventure has become a staple of my games as DM. Usually I mix it up with House on Gryphon Hill, either using that as a direct sequel or as an intersperal of linked scenes. I still have an audio recording somewhere of my first TPK in Castle Ravenloft and the subsequent meld into awakening in the Sanitarium in Mordentshire for Ravenloft II. Lots of fun. Well, for me anyway. It also gets used as a perennial one-off and is generally the adventure I use when I want to introduce someone to RPGs in general.
I loved the way it developed into a whole setting and I guess the highlight of the Ravenloft campaign setting for me had to be the whole "Grand Conjunction" era with that terrific return to Castle Ravenloft throughout its ages. There's a killer mini-campaign set around the castle in the making there somewhere. But that's another thread I guess...