Really? When was the last time you upgraded? It's been getting noticeably faster since 2008.
6 was amazingly responsive but sucked if you had to read/write anything (like, say, compiling). 2008 was average-slow at everything. 2010 had a go-away-&-make-a-coffee startup time that pounded the HDD, but after that was VERY fast given the complexity of the jobs it was given.