1) You'll miss enhanced mode in normal use too. All windows in Ambient etc would be drawn using so called 3D layers, using 3D hardware on gfx card. That would enable shadows and transparency effects etc, there wouldn't be any tearing in window moving, double or triple buffering could be used... etc..
Well, so looks like I'll have to wait for rv300 support anyway. I don't have plans to buy "another" old card!

I don't have more free space to store my "vintage" tech material.
It's the same core of the mobile radeon on powerbook g4s?
2) There will be nag requester and you probably notice the slowdown too
Well, I ended up seeing that. In the middle of the "Ultimate Pack" installation!

I had to install Tiger again and I have created 3 partitions:
1) ~50gb for tiger
2) ~20gb for MorphOS
3) ~10gb for OS9
But then I found that I needed another tiny partition to boot MorphOS. Is it possible to install morphOS on the 20gb partition without destroying the tiger installation? What's used for boot manager?