Hopefully none of this is spoiler stuff, but for caution...
From what I understand, once you start the dungeon you can't flit back to town to re-supply. You are limited to what you encounter within the dungeon. This can limit wizards because nominally the class feature of wizards that sets them apart from sorcerors is the freedom to choose what spells they add to their spellbooks. A co-operative DM who leaves spellbooks that just happen to have the exact spells that the wizard wants can easily solve this problem.
The reason you can't leave is the "dimensional lock" on the dungeon. You can't teleport in and out of the dungeon, and there may be limits on your ability to teleport within the dungeon. You also can't access extra dimensional spaces, so rope trick, secret chest, shadow walk etc are all out. This prevents the caster making bags of holding, hewards handy haversak, portable holes etc.
This dimensional lock also has the consequence that anything called into the dungeon is trapped like you. All summoned, called, and binded extra dimensional allies can't leave and will eventually turn on you. This makes conjurers a dicey prospect and really hurts the spontaneous summoning druid. (I can just imagine a druid that has just been mauled by a critter saying "But I thought the spell said summon nature's ally?")
Finally IIRC there is a recomendation that, in such a dungeon environment, movement hindering spells are too powerful. The module recommends DM fiat outlawing the use of web in the module. Entangle doesn't really apply because it is mostly a stone environment but that is recommended to be kept out as well. This one is probably the recommendation I have most problem with, but it is up to the DM. I only hope that each group who plays the module either all agree or all disagree with this recomended exercise of rule 0 and that harmony abounds at gaming tables everywhere.
A DM can choose to ignore these recommendations to help make it fun for any wizard or druid players. A sorceror can choose their spells to work around it. The restrictions are also logical and consistent with some of the premises of the dungeon. But as a player who favours wizards, in a party that has asked for a wizard, I felt a little disappointed that the module threw in a couple of obsticles to begin with.
I am approaching the WLD as a player. While my DM was good enought to warn me about all these hiccups, I haven't read any of the module itself. Those who have read it say it rocks hard. In light of these good people's opinions I am looking forward to playing in the WLD, it sounds like overcoming a little wizard pain will be worth it.