Out of curiosity what are your reasons for not running Leopard or why you prefer Tiger?
I find Leopard massively worse than Tiger. The UI is horrendous. The dock is way, way less functional - it is smaller and less clear (because of the fake 3D trick), the mess on the right side of the dock divider is appalling with folders stacking helter-skelter, the stacks feature took away the hierarchical view I use on a daily basis (to be fixed in 10.5.2, I hear), the icons for generic folders are horribly designed as if from 1980's.
Next, there are plenty of bugs compared to 10.4.11 - not surprising really in a new OS, so that's not knocking Leopard specifically, but it means delayed acceptance from those who like stability. Still, trouble with airport and so many other bugs just scare me away.
Next, Leopard is plain and simple a PIG. For the first time, an OS X upgrade is slower than the previous one. All others (Jaguar, Panther, Tiger) were faster than their predecessor on older machines, and Leopard is actually slower. Both my macs are PPCs - 1.5Ghz and 1.33Ghz (well within Leopard requirements), and I've read consistent reports of Leopard being slower than Tiger on those systems.
Next, Leopard just doesn't have any
new features that I really desire. Time Machine - meh, I use SuperDuper. Spaces - no use for me. Stacks is actually a step back. OK, quicklook seems interesting.
Meanwhile Leopard did not fix what was wrong with Tiger. My complaint about some features of Tiger has always been "promises and no delivery". Take Spotlight. Spotlight doesn't search
all system files and caches (which I find essential), can't find folders and can't do word searches in apps frameworks (for example, just try to find a playlist folder you made in iTunes - that's right, you can't). Spotlight can search for files which I have no trouble finding on my own (I'm pretty organized), but can't help with files I did not create and need access to (certain System files and caches etc.).
Bottom line, to me Leopard is a joke. Bring on 10.6... or will we have to wait for 11.0 for real innovation? Apple: please, hire more engineers and programmers, so that SOMEBODY can work on OS X, instead of being pulled off to work on the iPhone and all the other distractions... your OS X work on Leopard has been subpar, and power users notice it.