Currently Being ModeratedNov 28, 2012 7:33 PM (in response to billcb)
If you have a MacBook Pro 1,1 then forget it, stay on 10.6.8.
Use Carbon Copy Cloner and clone your OS X 10.6 boot volume to another blank GUID OS X extended formatted drive. (use the Secure Erase > Zero feature on the drive first to eliminate any bad sectors) this is your 10.6 clone so you can boot and use PPC based apps your going to lose going to 10.7/10.8 or to come back to 10.6 if you won't like the Lions.
Hold option key down on a wired keyboard to boot from the clone drive and check it out.
Next zero erase your entire 10.6 original boot drive holding option from the 10.6 installer disk
Reinstall 10.6 from the disks (same account name), reinstall iLife from the second disks and call Apple if you want to upgrade to 10.7 specifically but your MacPro 1,1 can go to 10.8 directly from AppStore.
Now your machine is bare bones, install your 10.8 compatible third party programs/upgrades etc.
On another drive setup duplicate Music2, Pictures2, Movies2 and Document2 folders and copy your files from the clone into them. Thus only on the boot drive is programs and OS X, no files.
You can command drag items like the original Documents, Music, Pictures folders off the Finder window sidebar and use the Music2, Pictures2, Movies2 etc there instead. However some programs will still try to save things automatically in the original user folders.
When you launch say iPhoto in 10.8 against the older 10.6 iPhoto Library, it will update it.
This sounds like a lot more work, but it's really giving you a solid footing, a stable fast system and free of crapola.
I always take a extra mile in being through to eliminate as many potential issues as possible, as it's cheaper and less hassle than cure, my machines always run well and fast, even Windows ones.
Currently Being ModeratedNov 29, 2012 5:07 AM (in response to billcb)
If you need to make space to upgrade to Lion, you should consider getting a new bigger hard drive. Plus, with a Mac Pro, you have expansion space to add hard drives very easily.