shaun:tried 10.5 and didn't like it.
It does take some getting use to I admit but, with tweaks here and there it is by far better than 10.4. I think that all applications will run on 10.5+ or maybe 10.6 Snowleopard by this time 2010. Quark included if, they ever get to version 9. But I doubt it with the rise of ID.