Harmy said:

the original FX are a huge part of the film's historical value, they were a great achievement at the time and redoing them in a computer totally takes that away, the matte lines and extra grain are just a natural part of the special effects technology of the time.

For the record, this right here is my exact opinion and, I think, makes the most sense. OT-Preservation is about the fact that, in 1977, how big movies were made changed tremendously, and the original special effects were part of that.