Quick Caution
One quick note before you switch to Leopard or above:
Some of your applications may no longer work. There are compatibility checkers available on line. I think, but can not remember, Apple has one on their web site.
Snow Leopard still allows Power PC type programs to run under Rosetta, but some Power PC & even Universal programs die. Lion won't run any Power PC programs. Rosetta is gone.
My examples from 10.4.11 to 10.6.8:
Parallels 3.x no longer worked. Solution: Switched to Virtual Box (and enjoying it- super fast & reliable) Cost = Free
Turbo CAD Mac v2: The company said it will not work under Snow Leopard & I was required to purchase the new version ($$$$$$) It works fine under Snow Leopard.
For 10.7- It will die for certain.
The worst part is that none of your existing tc3 files will open. You have to convert them to DWG or DXF before[I[/I] you upgrade. Then buy the new version ($$$$$$) & then import them back in. Each and every one. One at a time.
You will have, as I found out with conversions, lots of corrupted scaling & dimension issues. Some isometric views will be a mess & some layers disappear.
Solution: I have not found one. I have hundreds of drawings that will get destroyed by the conversion. My plan- Stall on 10.7 upgrade.
If it is legal (don't know)- Keep a partition with 10.6.8 for older drawings. As far as buying the new version- Ain't gona happen. IMSI decided not to provide any means for their older drawing to be opened in their new version, so I'll get someone else's CAD program, hoping for a more trouble free DWG import.
Microsoft Office 2004: Works under 10.6.x with a few glitches. It reportedly will not work under 10.7 (It is Power PC
Solution- I bought Office 2011, only because 2004 would not open some docx files & messed up some xlsx workbooks people sent me. Version 2011 works fine under 10.6.8- very slowly, but fine.
Other Programs: Some, especially my Canon Camera stuff, do not work under 10.6.8.
Solution- None so far.
I hope this helps you decide about the upgrade.
Paul