"What, objectively, is so much better and easier under Linux? Note, we're talking dev machine here, and not deployment serv"

Tool chaining. For me, the ease with which I can bang out scripts and makefiles and have the tools easily check out versioned code from rcs/svn and that I can pipe and redirect and have a host of efficient tools like grep and nm and objdump and more, and they all work together piping and redirecting to make exactly what I want in so many easily altered configurations. Release and debug and partial debug and static-checking build and more, with all the makefiles just text - so easy to alter and tweak and copy and share (and even have them configure on the fly, reading the output from the compilation and rerunning with extra warnings or debug symbols) and have them run commands themselves like sending eMails to everyone who is listed as an interested party on the source controlled spec list, and so much more. Valgrind is so useful that if I have to develop on a Win32 machine I get a version of it going under MinGw, and sometimes I run a Win32 debug under Wine on Linux so I can use Valgrind on it.

I sound like the biggest *nix dev env fanboy ever.