I hadn't noticed. But then, Tiger was removed from all my personal installations as soon as I got Leopard. With certain exceptions that's all I use.
Yes, I have tried several times to make Tiger the default OS on my G4s or G5s but I always end up back at Leopard.
If you have don't have a Core Image supported graphics card, 10.5 is slow until you update to 10.5.8. It seems they optimized CI software routines by that stage.
To be honest when running 10.5.8, I don't notice a difference in the UI between my 1.42Ghz Mac Mini with its non-CI supported Radeon 9200, 1.5Ghz PB 12" with the CI supported, but not totally accellerated Nvidia FX 5200 Go and my 1.5Ghz PB G4 15" with a fully supported ATI 9700 mobility card.
After I put an SSD in the 1.5Ghz PowerBook G4 15", I found Leopard boots quicker than Tiger from the same drive (53 seconds vs 68 seconds respectively) and Leopard performs better (and more reliably) in file and network operations.
Despite all this, Tiger does provide better battery life on the PPC portables and it does feel "lighter", so it's not entirely bad. I guess I mix it up depending on usage.