With Snow Leopard being about refinement, it's not surprising Apple's been making a lot of noise about benchmarks, with Snow Leopard comparing very favourably to its predecessor. We installed Snow Leopard over an existing Leopard install. It took 45 minutes to the second - pretty much what Apple told us it would - and then happily froze our Mac solid.
Luckily, all was fine after a reboot, and the OS does generally feel snappier than Leopard on the same system. Benchmark tests suggest this isn't just 'shiny new OS syndrome' either - shut down, sleep and wake times are reduced, copying to and from external drives is consistently faster, and even the Trash is quicker to empty.
The following list shows some recordings, based on averages of several attempts at each action.
Boot to log-in screen
Leopard: 34 seconds
Snow Leopard: 34 seconds
Leopard: 6 seconds
Snow Leopard: 3.5 seconds
Leopard: 4 seconds
Snow Leopard: 2 seconds
Leopard: 3 seconds
Snow Leopard: 2.5 seconds
Copy to external drive*
Leopard: 2 minutes 33 seconds
Snow Leopard: 2 minutes 22 seconds
Copy from external drive*
Leopard: 2 minutes
Snow Leopard: 1 minute 43 seconds
iTunes CD rip
Leopard: 5 minutes 13 seconds
Snow Leopard: 5 minutes 13 seconds
Leopard: 9.5 seconds
Snow Leopard: 7.5 seconds
* 2.23 GB of data, 31,560 items
Some swift mental arithmetic showed the leaner, meaner OS had returned about 20GB of hard drive space, and general performance with most applications over several days was, at worst, equal to Leopard. A few applications on our test system fared poorly, though: iPhoto in particular has major focussing problems, and Office 2008 was sluggish at first, but eventually kicked into gear.
Photoshop CS4 also exhibits quirks, such as inconsistent behaviour when dragging items to its Dock icon from Finder, and tool cursors reverting to the standard mouse cursor when the mouse button is pressed.
Most damning is Apple's hate of PowerPC seeping through - Rosetta is not installed by default, which seems a pointless barb. Instead, you get a dialogue box thrown in your face when booting a PowerPC app, and, on your confirmation, Mac OS X grudgingly downloads and installs Rosetta in a painless fashion.
More impressive is Safari's sandboxing of plug-ins. While it'd be a huge fib to suggest the browser's now bulletproof, we've had one crash since installing Snow Leopard, which is a marked improvement over Safari on Leopard.