I took the plunge to be part of the 9% (or so they say at the time of writing this) of Mac OS X early adopters. With Tiger I waited a while. I figured with Leopard, why not. Check here for some of my experiences of running on a PowerBook G4 with 1.5 Ghz processor.
I have to confess, I was a bit worried about that being on an older 1.5 GHz powerPC they old Leopard may run more like a slow dog than a sleek cat...
The Install - I had read that this should take a few hours. I was surprised when I thought It was going to take about 30 mins.... but that must have been the first step of copying/unzipping the files. The next step took a couple of hours. I am not exactly sure as I walked away. That said, when I came back Roarrrrrrr... I was ready to go!
So I started checking out some of the new features:
Performance - still making up my mind. I think it's OK, things were a bit slow to start off with, either I have adjusted to the slowness or it was things compiling/caching the applications for the first time.
The finder - this is what i was looking forward to the most. The ability to browse through images in a slide-show like way is very cool. Leopard is really catching up to Windows Explorer/Windows XP. That said, I am over the moon to get it. Especially as i prefer to keep my images on a shared server and not in iPhoto.
Desktop - Wow, I have cleaned up my desktop. Firefox puts it's downloads in my "downloads" folder. The stack on my dock is cool... it definitely reduce clutter and an helped reduce an untidy desktop.
I also created a new stack for "Media Apps" and created aliases and placed all my apps like iMovie, iPhoto, Flickr Uploadr, GIMP, OmniGraffle into this folder. They now appear as an expandable stack - the net effect has been more room on my dock.
Some improvement could be made to make it easier to create new stacks... I had to create a folder, add aliases and then dragged it to the dock. It would have been nicer to be able to drag existing dock icons into a new stack.
Spaces - ok, so this existed in with Expose... but I never really used it. There are some improvements where you can assign specific apps like Firefox, iTunes etc to specific spaces. So I am trying to use it. The cool things is it reduced clutter - eg iTunes, Firefox and NeoOffice/Word are all assigned to their own spaces. This allows me to maximize the apps and look at them in on nice clean screen.
Safari - I use Firefox. So I have not played with the new Safari.
Mail - I use my Yahoo mail. I prefer being able to access my mail from any PC... so browser based mail suits me well for my personal mail.
iChat - I have yet to have a video conference with the new iChat. I have found Skype video and voice to be more reliable. I will check out what the new iChat will be like when I find someone else on Leopard.
TIme Machine - I have a networked Lacie drive for my backups. At this point of time Time Machine will not work with a networked drive 
. I have my USB drive as a backup to the Lacie. So I will need to purchase another USB drive if I want to leverage this. Not sure why TimeMachine does not work with a Network Attached Storage (NAS), perhaps it's performance?
Parental Controls - my kids are 3 and 1.5 yrs... so no need to try this out yet. I do need a key board protector as they like ripping keys off the key board.
Boot Camp - it's a PowerPC... so no need for that 
All in all it's been a good experience - Go the Leopard Go!
