I'd like to hear more about this -- what was it about the product that turned you off? I really don't remember it; I think I cribbed the map from it for something once but that was the extent of my experience.
It was probably one of the worst products I'd ever bought. I won't say it was the worst product I've ever seen, because I've seen a lot of bad RPG products, but it was really really bad.
1) Supposedly being for 1st level PC's. The local village contained a fairly large number of 10th level NPC's occupying minor jobs like bartender and town gaurd. This raised the issue for me of what any one in the town wouldn't bother to go collect the very significant treasures from the local dungeon despite challenges which to them were trivial and represented little danger. It was typical Ed Greenwood DM PC's infesting every little corner of the world. Every spot required NPC's to outshine the PC's by an order of magnitude.
2) The Haunted Halls themselves represented very little content. Thirty-two pages gives us fewer than 32 encounter areas and perhaps a session or two of gaming.
3) The encounter design was primitive in the extreme. The dungeons was just a random collection of randomly connected rooms with contents unconnected to anything really. The 1e DMG random dungeon generator with only the mildest of guidance could have produced the equal of it. There was nothing here really that was above the level of quality I would expect from a 15 year old DM. There was nothing here I would have considered as an editor remotely publishable, except that there was a big name attached to it. I bought a product and got something that was not only below my standards, but would have been considered below my own standards 4 or 5 years prior. That to me was a complete waste of money.
4) Beyond the complete lack of refinement and skill on display, the encounters themselves where Monte Haul and munchkiny. I seem to remember that the 1st level of the dungeon for 1st level characters contained as a treasure a morningstar +4 (or something of the sort) and provided as a foe a Mummy. Challenge level and reward was all over the place.
5) The best thing that can be said about the whole book was 'Winged Housecats', and if that is your best selling point, then something is really wrong.