TrustedReviews have looked at the Apple Mac OS X v 10.5 - Leopard.

All in all, it's hard to view Leopard as much of an advance on Tiger. The interface improvements are a mixture of 'great' and 'meh', while the new features don't really add much beyond tweaks to your daily workflow. The feature with the ability to really blow you away - Spaces - is switched off by default, and probably won't be found by the majority of people. So whilst Leopard will undoubtedly sell tonnes of copies (quite apart from the fact it will now ship with all new Macs), it's hard not to feel that, given the system's delay and hype, Apple has delivered too little too late - with too many bugs, to boot. Perhaps it's time for Apple to start thinking about OS XI?

Apple Mac OS X v 10.5 - Leopard Review