Setup Assistant from PPC OS 10.4.11 to new iMac

You should know that you can't use Migration Assistant to restore a Mac with Mac OS X Tiger (Mac OS X 10.4) onto a Mac with OS X Lion or OS X Mountain Lion, so you have to follow other steps manually in order to restore your data to your new iMac. See "Migration from Mac OS X v10.4 Tiger to OS X Lion" > http://support.apple.com/kb/ht4889

Another thing you can do is to copy the data you want to transfer to your new Mac onto an external disk, and then, connect the external disk to your new iMac and copy it to the hard drive.

If you want to know if the applications you have on your PowerPC-based Mac will work with your new iMac, open Applications folder, right-click the application you want to get the information and choose "Get Info". Then, look next to "Kind".

If, next to "Kind", you see "Application (Universal)" or something similar, you will be able to use that application with your new Mac. However, if you see that it's a PowerPC app, you won't be able to use the application with the new Mac

Incompatible files, if they are PowerPC ones, won't do anything to your Mac because Mac OS X will refuse to open them. However, if you try to open an old Intel application that may not be compatible, you may get kernel panics... I think you should try to migrate your data

You probably can move "files" over, such .doc, .jpeg and many others over to your new Mac. That should be fine.

But I wouldn't move a single app or anything like that over. Yes, as mende1 said, there are many Universal apps that will run, but you probably didn't update them to keep them running on Tiger. I just can't imagine that there is a Tiger app that you will want to keep, since things written now are just optimized for a much more advanced OSX.

More than that, you'll be spending loads of time finding preference files that you'll want to keep and other things.

Really, spend your time finding modern versions of apps, even if you've invested a lot of money in some ancient version of Photoshop or something.

See Pondini's Setup New Mac guide. AFAICT, there's no conflict caused by attempting to run PPC apps in Lion/ML. Software related KPs usually occur from conflicting kext files.

If it was me, I'd migrate everything, using the first boot Setup Assistant. Then, remove anything that won't work (PPC apps). The AFAICT is based on beta-testing every cat from Jaguar on up to ML, so take it for what it's worth. Good luck. The new machines aren't in my future, since I have no use for iOS stuff and still use PPC apps.

In my testing, either should do the job, although it's easier from an ext HD.