It really depends on the area where you live. Several of the builders that are mentioned in this post are clients of ours. I have had previous discussions with some of the on-site customer service representatives, and their experience was that, in the areas where real estate was more expensive, they would use more experienced and more expensive subcontractors (and better components) to do the work. However, in areas where the real estate is generally less expensive (take, as an example, Victorville), the builder will need to hire cheaper labor, use cheaper parts, etc., in order to meet their desired margins.
Regardless of whether you live in an expensive or less expensive area, the fact is that these builders are all out to make a profit, and will always try to find ways to save money in order to maximize their profit. Also, given how quickly these homes are built, it's not surprising (to me, at least) that many of the new homes exhibit problems with fit and finish (or, in some cases, with the soils).
However - this is just my $0.02 based on what folks who have worked for some of these builders have told me. I live in a home that was built by one of these builders, and which is now about approximately 6 years old. Although some of the components have needed repair or replacement, I have no major complaints with the quality of the home. On the other hand, I know of a condo that was built in late 2010 where the HVAC and garage door opener are already exhibiting problems. Both are located in the same city.
