Historic preservation is good for the economy and is one of the best economic development tools available. Neighborhoods with historic districts typically grow in value more than identical non-district neighborhoods.
Heritage tourists tend to spend a lot more than non-heritage tourists, and they tend to stay longer than non heritage tourists.
Historic rehabilitation returns much more to the community than new construction. Rehab uses a lot of local labor New construction uses more prefinished materials imported from other areas. The local labor tends to buy their materials locally and, of course, the buy lunch near the job. So preservation is good for local job creation. New construction creates many fewer jobs.
An interesting study by the GSA indicates that the cost of heating, cooling, and maintening historic buildings is less than new buildings - largely because of better than average construction.
The same study by the GSA indicated that most employees are happier in historic buildings than in new buildings (mainly in mid-size buildings).
A key question is whether the building or district is "significant." Should people be able to see how people lived in 1840, or 1920, or 1960. If there are lots of exampes (e.g. a 1950's subdivision), preservation of one neighborhood may not be as important as preserving the last grist mill in the state.
A lot of people are trying to use preservation as a way to keep out new development. That's not good because is ruins the basic reason for preservation.
The preservation lunatics are right when they want to preserve a very significant historic building in its original form. You lose a piece of that building, and you lose the ability to tell its story. However they often use the same level of review for less significant buildings - giving preservation a bad name. You need the original windows in an 1850's store. You don't necessarily need them in a 1940's subdivision.
End.