Terrible? There's more work there doing stuff like disabling eyecandy bollocks and tweking it so it'll actually run at a usable speed on real hardware, than there is to work your way up from standard 3.1.
The exception to that is Cwb because that was made by someone you could describe as "sane".
Which environment are you talking about?
Amikit, yep you really need an '060 to make this shine. And it doesn't look or feel like an Amiga. But under WinUae its great and looks better than any Linux theme I've seen.
Amigsys and ClassicWB have versions optimised for whatever hardware you have. I have a 2 meg version of classicwb and it flies on an A1200, and has most of the essentials covered.
AIAB is great too on low end hardware
Really an '030 and some fast ram with classic wb will give you all the functionality of AmigaOS 3.5+, with all the patches that would take you a lot of time to get done yourself, and its faster.