I started the group at level 2 after reading so many posts about the meat grinder factor of this AP, and seeing WC as the number 2 killer of the 12 adventures.
Using a few house rules -
1) At 1st level, characters choose a number of skills equal to 1 + Intelligence bonus. These skills are always considered class skills for that character. I did this to allow characters to pick up skills they wanted for their characters that don't necessarily belong to their chosen classes. Not giving them any extra skills, just a broader selection when choosing their skills.
2) Following one of the things I like in the upcoming 4E, a few skills are being combined. Hide and Move Silently are now Stealth. Listen and Spot are now Perception. And Open Lock & Disable Device are now one skill, I just haven't made up a name for it yet.
3) Fighters are modified. I am allowing them to use feat retraining starting at level 4, for fighter bonus feats only, similar to the ability of a sorceror to swap out spells for new spells. Fighters also get to choose a signature weapon at 1st level, and receive specific feats in the Weapon Focus tree for free as they level up as fighters. This option is available ONLY to characters who start their career as fighters, and the bonus WF tree is only for Fighter levels.
4) I am allowing pretty much all of the splatbooks, including Bo9S. However, anything from those books; prestige classes, feats, spells, etc., will be reviewed by me on a case by case basis. Some feats and spells have already been modified or outlawed. For example, the transposition spells from the SC are banned, and the Mage Slayer chain has been altered.
5) Tumble. I have never liked the flat tumble DC. The fact that you can just as easily tumble past a 20th level fighter as you can a 1st level wizard annoys me. Tumble now has a scaling DC, 10 + opponent's BAB to pass them and 20 + opponent's BAB to move through them. Certain feats can raise this DC.
Those are the only ones coming to mind immediately.