“As I’ve learned more about Leopard, it’s become increasingly clear where, exactly, those two-and-a-half years of development time went. Leopard is absolutely packed with improvements. It seems that not a corner of the OS has gone untouched,” John Siracusa reports in his comprehensive review for Ars Technica.

“Perhaps that’s not as clear to the casual user who just sees the surface changes and the major new features in Leopard. But even in that case, there’s more than enough to recommend it. if you’re wondering whether you should upgrade to Leopard, the answer, as it’s been for every major revision of Mac OS X, is yes,” Siracusa reports.

“I’m most excited about Leopard’s internals. They’re the star of this release, even if they don’t get top billing. There’s a good reason we’ve already seen so many prominent Leopard-only software announcements. This is where developers want to be,” Siracusa reports.

“Leopard’s pull on developers will translate into better applications for users… eventually. In the meantime, I’m hard pressed to think of a single Mac user I know who wouldn’t benefit from Time Machine’s hassle-free backup magic. If you’re looking for one reason to upgrade, this is it. Yeah, backups are boring, which is why you’re probably not doing them regularly right now. No more excuses,” Siracusa reports.

“The stage is set for Mac OS X 10.6 to triumph beyond the bounds of its ancestors. In the meantime, it’s the Mac development community’s opportunity to shine. Whether it reigns for two and a half years, like Tiger, or even longer, I’m looking forward to my time aboard starship Leopard,” Siracusa reports.

Full comprehensive review – highly recommended – here.