I have been using Debian Lenny on my iBook for a few weeks already. It is great so far. It took some time to configure, but after that it is largely smooth sailing. Here is some notes about my experience with it.
I used Debian PPC netinstall for installation. That means command line interface only at first stage, no GNOME, or KDE. The rest was downloaded later through internet connection.
The iBook G4 only has 30 GB hard disk capacity. That is too small for dual boot for me. So I moved all important data on previous Mac OS X installation, readied it for Linux-only installation. Then I wiped out all the space on the hard disk.
The installation process ran with little problems. I decide to defer system updates (which can be done at installation time), to save time. After the installation finished I was greeted with bare, black screen of command line console.
Next step was to chose a desktop environment. I had experimented with KDE before, and didn’t really like it. So I installed GNOME. I only selected the core components (gnome-core), and picked the rest as needed. It took quite long time to stop fiddling with the applications and components. In the end, I am left with a nearly standard GNOME desktop, with some small modification. For instance, I choose Firefox, er, Iceweasel as default browser (not epiphany). I also don’t install gnome-games. The only game that exists on my iBook is Battle of Wesnoth.
Lenny uses GNOME 2.22, not the newest version (which is 2.24). This might be a minus for some people which wanted the latest and greatest. But I have been using it for a time (with Fedora 9), and I am quite content with it.
Debian Lenny itself is still yet to be formally released. But it is quite usable, and stable. There are some problems, but not too critical.
The first problem is NetworkManager, that, you guess it, manage networks automatically. I use it with my Fedora installation on my other laptop. I quite like it. The killer feature for me is the ability to handle 3G modem connections. Unfortunately this feature is only found at later versions of NetworkManager, that is, in 0.7. Debian Lenny includes version 0.6.6, which might be stable but already outdated. The solution is to enable experimental repository, and install the 0.7 NetworkManager from there. This forced me to learn about running mixed systems, and the art of apt-pinning.
Another problem is power management. GNOME power manager apparently work without problems in x86 architecture. But it has problems with PPC, at least on Debian. Lenny with gnome-power-manager failed to suspend on this iBook. After some googling I decided to uninstall gnome-power-manager and use powernowd and powerprefs for power management.
There is also lack of decent Flash plugin. Adobe don’t have their proprietary plugin for PPC Linux, and both swfdec and gnash don’t really cover much flash sites that well. Fortunately, Flash isn’t that critical for me.
Overall Debian Lenny on the iBook is quite a pleasure. It is very stable, and I am yet to crash it (unlike Fedora 9 on my other laptop). It feels faster and responsive than Mac OS X Tiger. It handles my ZTE 3G modem adequately (but better than OS X).
Unlike before, I think I will keep on using this Debian installation on my iBook.