Clean Install and Time Machine backup?

Probably. I create a compressed disk image of the disk(s), before i erase the entire disk. Later, after the clean installation of the new OS, i can mount this disk image and can copy all files which i need from this mounted disk image to my new Mac OS X installation. I recommend that you do not copy things like applications, plugins and so on, because these can cause problems on the new, clean installation. I reinstall all apps, plugins and so on.

More info:
Mac OS X v10.5, v10.6: How to back up and restore your files-Using Disk Utility:
http://support.apple.com/kb/ht1553

Ignore the Restoring the backup disk image's contents to your internal Mac OS X disk section.

Btw, Time Machine backups are not reliable enough, IMHO.

EDIT: Make sure that you can mount the backup disk image, before you erase the original disk!

 

As I recall when you first boot a fresh OS X install, it allows you to customize what gets restored with 4 choices. If you select the User data only, you will still get user preferences and such for applications, but those are easy to find and delete if you need to.

Everything else you will want to set up or install fress (applications).