I think Sean might be a tad disappointed in one of the Leopard features called Time Machine. It would appear the new backup feature didn't live up to his expectations. Here's a quote from his blog entry:
"But with two-and-a-half years of development, Apple has surely gotten backup right in Leopard, right? Time machine certainly demos well... Having installed it tonight, however, I can tell you that Apple's advertising is correct. Time Machine is a "giant leap backward."
See http://blogs.technet.com/seanearp/archive/2007/10/27/time-machine-apple-s-advertising-is-correct.aspx for the entire post. Sean makes some good points so it is worth a read even if you have no plans to ever run a Mac and OS X v10.5.