Tiger doesn't need anywhere near 4 GB if you deselect all the additional languages and printer drivers during the installation, and it doesn't "limp" in half a gig of memory, in fact it absolutely flies on my Mac - boots in 40 seconds, which is in fact faster than some brand new PCs, the interface is extremely responsive and smooth, Spotlight is fast, and all the latest software like Adobe CS3 and iLife '08 works great!

As for championing older software, yes, it may have its places, but I really don't see the point in going for older when newer does so much more for no major performance penalties.