Our solution consists of 41 projects (both vb.net and C#). Our configuration is VS2005 on a Dell Precision 390's with 4GB RAM, 2x SCSI (10k RPM) HDD's using RAID 0 and a Core2Duo Extreme 2.93GHz CPU. Compilation time is minimal and VS2005 runs FAST! Beforehand, we ran on HP Pentium 4 2.8GHz HT with 2GB RAM and 1x SATA 7200 RPM HHD's and everything was SLOW as a snail on ritalin! We lost hours a day to compilation time with VS2005. The new hardware has made coding a pleasure again, with zero hassles and the solution takes about 20 seconds to compile = much happier developers :) Even with the high cost of the new hardware, we calculated that we would break even within 2 to 3 months due to the increase in productivity and not losing as much time to compilation.

I do not know for certain. It is my suspicion that the #pragma once will cause the file to be added to a table that it has already been processed, whereas the #ifndef does not necessarily preclude reparsing of the entire header, as one does not necessarily include or preclude the entire file within the confines of an #ifndef/#endif set. The #pragma once, however, seems to imply, "hey, once you read this file for this compilation unit, don't bother reading it again". I favor adding the #pragma once if I now a header would never require reparsing within a single compilation unit. I prefer to create headers that do not depend upon such reparsing activity.