Sir Launcelot du Lake sums it all up nicely in his review: Strahd's Possession is a mixed bag; the good storyline, soundtrack and full speech throughout makes it worth experiencing.
Some aspects of the interface and the time wasting puzzles are quire irritating. AD&D players, already used to the insidious puzzles from previous installments, should be able to overlook it and enjoy the game. Hopefully DreamForge will take note of the shortcomings when they use the same engine to write their next game - AD&D Forgotten Realms: Menzoberranzan.
Review By HOTUD
English 
Comments and reviews
Yes, the level draining is annoying and can't be undone. Negative plane protection on the first two characters does help somewhat. Just check after killing a vampire or a wraith whether the protection is still up and if not, renew it.
The only problem I had with this game (CD version) is a gameplay issue - there are no restoration spells, scrolls or potions in the game. So if you get level-drained by an undead (and you will, this game is loaded with them!) you have to either restore an older save or play until you level up. Otherwise, an awesome, atmospheric game that, although shallow plotwise, plays to the strengths of the campaign setting and the otherwise excellent gameplay.
That game is buggy as hell and the disk version is unplayable because of that.
Try to get the CD version from the AD&D Masterpiece Collection. That one is properly patched and almost bug free.
Game plays fine until I get to the cavern under the Ivlis. As soon as the first skeleton makes it's way onto the screen, it freezes saying "trying to load file 93/3" or some other number based on where in the cavern I saw the thing. Every time, every circumstance, as soon as a skele pops up, the game freezes. What gives?
No comment nor review for this game at the moment.