My $0.02
I just recently bought my first Mac (PB 15") after having run Red Hat on a Dell laptop for the past 2+ years. Since Yellow Dog is based on RH it should be similar.
It is very easy to get a basic system up and running, as long as it's the only operating system on your box. It will actually handle a dual-boot setup well, but you first have to split up your partitions manually for that (the installer can't/won't resize your existing OS X partition in other words). The install is a matter of clicking through a bunch of screens where you're selecting preferences. Piece of cake.
After the install you will have a nice, easy to understand system. I loved Linux... except for those occasions when I HATED it.
- You won't currently be able to use your Airport Extreme card. A regular Airport card on an older system will work fine.
- USB and Firewire work well - but it can be a pain in the neck figuring out just what the heck /dev/???? to use to actually access your USB or Firewire device.
- Your ATI video card will work... but hardware acceleration won't.
- Bluetooth won't work.
- "Sleep" doesn't currently work.
- Check YDL's support pages for the other caveats.
Basically if you're a tinkerer, or if you've got old hardware that doesn't run OS X well, then go ahead. If you've got a big hard disk and can spare ~10GB for a Linux partition plus room to play, go ahead. It can be a lot of fun - but just be aware it can be very frustrating too. I'm glad I've had the "Linux Experience", but I'm doubly glad now to have discovered OS X. It pretty much allows me to still do the stuff I found useful in Linux (especially when you install Fink), but without the occasional bouts of extreme frustration.