I think those that say "if you don't have $x, then you can't AFFORD the house" are being too simplistic. If you're financially stable and the cost of the mortgage is about the cost of rent, you can probably AFFORD the house. The mortgage crisis was exacerbated by 100% LTV ratios, but I think they were caused by speculators (even if they didn't recognize they were speculating) who assumed home values would go up sufficiently to make required refinancing (because the interest rate on the variable loan was going to go WAY up) easy.
If you're getting a 30yr loan with a fixed interest rate, I really don't see the problem with high LTV ratios (even 100%, but those seem hard to come by these days!) if you're willing to stay for the long run.
It always seems a shame that when you can finally AFFORD a large house in a nice neighborhood, the kids aren't living at home any more, and there's really no need.