Most things should be similar. Proprietary drivers (like for graphics cards) obviously won't work (though the firmware should, I reckon, since that's independent of the host CPU). Proprietary software in general probably won't work unless you can convince the vendor to ship a POWER build. Even some FOSS might not work fully (or even at all) if it relies too much on specific architectures (in particular, I know V8 - and therefore both Chromium and Node.js - only very recently got POWER ports).
I personally run OpenBSD on all my (Apple) PowerPC hardware; it seems to work a lot more reliably than the Linux distros I've tried (in particular, I remember the install process for Debian being rather painful on PowerPC due to OpenFirmware, while OpenBSD is just as easy as it is on x86: mash the Enter key until you have a working system; at most, I sometimes need to tweak some boot settings at the OF prompt, namely if it was previously running OS X).
I have a PowerBook G4 that was at one point a daily driver, plus an eMac that was running at one point but needs a new hard drive; those were/are both in desktop roles. I also have a Power Mac G5 and an XServe G5 in server roles. All of them have OpenBSD 5.9 installed (except the eMac, which had OpenBSD 6.0 installed before the hard drive failed).
The XServe and Power Mac are in storage right now, but I'd like to get the Powerbook upgraded to 6.1 eventually (I want to stick full-disk encryption on it, too, so I'll probably just blow away the existing install and start from scratch).
6.1 for macppc doesn't ship with any web browsers except for text-based and Netsurf sadly. It struggled on my 1Ghz iBook speed wise too. I am going to give it a fresh look on a DP 1Ghz Quicksilver too.
I personally run OpenBSD on all my (Apple) PowerPC hardware; it seems to work a lot more reliably than the Linux distros I've tried (in particular, I remember the install process for Debian being rather painful on PowerPC due to OpenFirmware, while OpenBSD is just as easy as it is on x86: mash the Enter key until you have a working system; at most, I sometimes need to tweak some boot settings at the OF prompt, namely if it was previously running OS X).