I am currently (and happily) using v5.1 of the compiler. Is v7.0 much faster to make it worth upgrading to?
5.0 compiler, in the Pentium III days. We didnt have much of a concept of the Pentium 4 processor. So, yes, quite a few optimizations have been implemented for Pentium 4 and also the Intanium 2 processor in the newest release of the Intel compiler. There have also been many other optimizations.
Please note that the 7.0 version of the Intel compiler can sit next to the 5.0 compiler (You choose it in the dialog box on Windows and you may need to install it in a different directory on Linux). Please see if it works for you.
You can also compare reviews available on the web site, some of which compare older versions of the Intel compilers. For instance, the Coyote Gulch has older reviews available - see http://www.coyotegulch.com/reviews/index.html.Notable, are the improved C++ optimizations available in the latest compilers.