First, Quark 5 is suppose to be Carbonized on release. Remember the expo?
As for adobe, they are taking a long time because A) they are building things from the ground up to run nativiely in cocoa, because they want to do things right, and not just port it over. B) They are very understaffed right now since they are having financial problems, C) GoLive 5, Indesign 2, Illustrator 10, and After Effects 5.5 are all OS X Native. The reason photoshop is taking so long is because it's a TON of code. Probably their biggest application, and re-wrting it from the ground up is going to take a while, especially being understaffed.
My old machine, an original iMac DV SE ran OS X.0.4 fine with 256 megs of ram, and it ran amazingly smooth with X.1 and even smoother with 10.1.1. I went ahead and got a Dual G4 800, and it runs great. I even run UT in classic and get at least 45+ frames a second with an occasional burp or two.
At work I run a 350 B&W G3 as my work machine, and a Beige 300 G3 as a test server running Filemaker and Apache full force using 10.1.1. I have had no real problems.
Also, a lot of my Unix and Linux friends love OS X. A few of them have bought older machines to play with it.
Where I work, which is predominately mac, we are still on 8.6. Why? Because we have an ancient 4D database and it won't run on anything higher. When we finally upgrade, I have the duties to upgrading all the machines to OS X, which runs good on the 400+ powerbooks.
I really don't know what all the fuss is about. Mainly people that don't want to change, don't want to learn something new, or just grinches.
My two cents.