Just to add to the confusion, as part of the silver anivaersary celebrations, they also released an adventure called simply 'Ravenloft', which was the original I6 with the stats updated to 2e, but not (presumably) the other changes that House of Strahd had.
Actually, the "Ravenloft" adventure was released after House of Strahd and has a few tweaks in it that HoS did not have.
The module is dangerous enough on its own that you could leave out the Fear, Horror and Madness checks. As an experienced Ravenloft DM, I'd suggest leaving out Madness anyway, that's never really worked in a way that contributed to the game (its more of a game-breaker, game ruiner kind of thing), but Fear and Horror checks work quite well, but they are optional. If the PCs role-play their characters well, the rules suggest that the DM doesn't make the players roll. But if the players are all "oh, another vampire, ho hum!", or something along those lines, that's the time to have them roll. Then again, with the PCs at mid level and up for these games, they'll pass almost all of their Fear and Horror checks anyway.
One thing that did come to mind about Ravenloft vs. the other versions, is that Ravenloft has scaled up considerably. For the original adventures, PCs are 7th-9th levels, in Ravenloft, they are 10th-12th. So, they might last a little longer, have slightly better odds at survival--at least until they get to Strahd at the end (16th level Vampire Necromancer).