The builder we had was relatively decent in handling our concerns, but I find the service significantly drops off the minute they hand the keys off to you. If there any big items found on the PDI, make sure you hound them to get them fixed properly.
We're into month 5 and there are some things they've come in to fix several times but have failed to fix... Cosmetic things so I'm not too concerned, but wasted time taken off from work none the less. The other thing is, what other people have said about Mattamy roofs is absolutely true - so shabbily thrown together. A home inspection for your 30-day warranty items is highly recommended if doing an outdoor roof inspection is part of the package.
With regards to your comment about the hallway, I tend to agree with you. I find that the hallway is quite narrow (that's actually kind of why we elected to keep the foyer "open to above" as opposed to putting in a nook/room/washroom, but it's manageable... If you choose an "end-banister" like we did, however, the logistics of getting bigger things in and out of the house might be a bit more difficult.
Please excuse the crude MS paint drawing, it was the best I could do at work
Essentially the "hat" portion of the post is quite pointy, and protrudes a bit too much. In turn, it kinda catches on whatever goes by... Furniture, clothing, etc.