I lived with Leopard as my only operating system during 28 October - 8 December 2007. Yesterday, I spent a few hours reverting the data on which Apple's Mail and iCal depend into formats suitable for Mac OS X v. 10.4, aka Tiger.

In terms of the national steroid pastime, Leopard is a triple. Spotlight is an amazing paradigm shift and has the potential to make even partially implemented archival systems useful. For most people, I imagine it could even replace any need to organize anything at all. However, for top-level browsing, one will still need to have some kind of filing system in place. Also, the Mac OS file system has not evolved into a database model so one has to think through and implement a meaningful hierarchical structure for one's files.1

Cover Flow in the Finder combined with Quick Look makes directories that contain large amounts of data browsable. For example, I use software that captures images of all my screens several times a minute. I frequently retrace my computing activities, reconstruct the occasional lost document, and reload poorly-remembered web-accessible resources using the images that software captures. Cover Flow and Quick Look make browsing those files much easier than under Tiger, even with Photoshop to help me browse those files.

However, Leopard has a few fundamental problems and the one that prevents me from using it is that it will not let go of network volumes which contain data that has been used by Mail and (I suspect) iCal and Address Book. The only workaround seems to be logging out. While such a workaround is not a problem for a client machine, my main machines are Internet-facing servers, and a server that cannot unmount network volumes is unusable. My guess is this problem would manifest for third-party programs, but I don't have time or need to test other conditions. As far as I'm concerned, Leopard was born broken.2

Finally, with my particular passel of software and settings, Mac OS X v. 10.5.1 seems to be made of memory leaks. Within ten hours, the swap space balloons to over 5 GB.

When I finished reverting my data yesterday at about 11 pm I had this profound feeling of safety. Tiger as of 10.4.10 (the reports on 10.4.11 are not good) is solid. Mac OS X v. 10.4.10 easily achieves weeks of uptime, no log outs required. Third-party developers had achieved a deep rapport with the quirks and features of Tiger's APIs, so much so that even big-time no-nos (Unsanity, I'm looking at you) did not destabilize a machine to the point it could not be used. As a case in point, I run Unsanity's WindowShade alongside Final Cut Pro, DVD Studio Pro, Mail.app, Apache, and a moderately customized PERL installation. No problems.

So, I'll wait for 10.5.2 to hit. I think Leopard is great if you're doing nothing but wordprocessing surfing the web. But if you rely on your machine as a server of any kind, wait until Apple fixes what's broken.