I don't think Leopard deserves the flack it has gotten in this thread.
Let me just state that Leopard's biggest fault is that it was the first version of OS X to run slower than it's predecessor, Tiger. Plus if you were reliant upon using the Classic environment to use Mac OS 9 apps, that was axed with Leopard as well. MobileMe also sucked but I consider that not so much of an OS problem as it was a 'services' problem.
That being said, it is my OS of choice for my PowerPC Macs that I use. Even after 19 years of use it still feels fresh and modern. Heck it introduced many things like Quick Look, Spaces, Time Machine, Smart Folders. I prefer how Leopard handles Spaces and Expose vs any version of Mission Control. It's window chrome also suits my tastes better as it's neither too light nor too dark as is the case with most modern OSes are. Though it runs slower than Tiger on my systems, the performance penalty is really negligible especially since all my PowerPC macs now have SSD's. If anything they now run as fast or faster than Tiger just on that factor alone.
There were a whole class of applications that were written to take advantages of the changes in Leopard vs that of Tiger. Bento is one prominent example that comes to mind. IMHO much of the greatest Mac software was written between 2007-2009. One of the reasons I still have and use PPC macs is so I can run software like iWork 09, iLife 09, Apeture, Pixelmator 1.5, Logic 8 Pro, Final Cut Studio 2, Bento, iTunes, Scrivener 2, et. al. Sure I can use their modern equivalents on my Apple Silicon macs, but I enjoy the older apps more, and I'm not bogged down with constant notifications and distractions like I am in more modern OS environments.
Never once in my 19 years of using Leopard did I ever feel it was unfinished. By the time the point updates reached version 10.5.8, Leopard had significantly closed what performance gap remained between it and Tiger. Suffice it to say, that in my experience as someone who still uses Leopard, it is a great OS. Snow Leopard optimized it, made some minor UI tweaks, and introduced new core technologies for the future, but Snow Leopard wasn't a correction of mistakes of Leopard, nor a needed reversion of poorly thought out changes. Though I was miffed at the time of PowerPCs not getting an official release of Snow Leopard, in hind sight it makes sense.
AI features aside, I view Golden Gate as a much needed correction for the many flawed UI changes made in Tahoe. To me, Tahoe's UI issues, plus it's lack of Firewire support and inability to connect to AFP shares ended up making it a non-starter for me. I have put GG in its own volume and so far it seems like my major usability complaints have been largely addressed. It is also more performant than Tahoe. I will probably keep a dual-boot setup of GG plus Sequioa.
