Sorry to have let my end of this die for a time, but I went from posting here to browsing discussions.apple.com, where I gathered that 10.6.8 might not be too ambitious a goal for my older machine, especially since I want to edit video. I thought that was taxing enough, without the latest and greatest OS I might not really need possibly bogging it down. Am I too cautious?

Anyway, I'm not too proud to admit I just forgot my post here, but I am glad to see this discussion, because it confirmed some of what I've ben thinking and, as always, directed me to ways to manage my Mac better.

By way of preparation for the upgrade, I have been using Time Machine for a long time, even recovering from some accidental deletions in the past, so I felt covered there, and I let DiscWarrior 4.2 work on my disc's directory, which was not bad anyway.

Then I tried running iDefrag 2.2.0 with its "Quick (on-line)" algorithm and found my free space fragmentation rose to 98%.

Thinking, fragmented or not, more free space would help the installation, I nudged it from 35 GB up to 42 GB (with some help from OmniDiskSweeper; thanks for suggesting CleanApp, I must try it) by deleting some duplicate video files etc.

Then I learned how to use iDefrag off-line and, still being cautious, I chose the "Compact" algorithm, said "to improve free space fragmentation without running a full optimization", and reduced the fragmentation to 1.3% (while leaving the rest of the disk pretty fragmented; this took about four hours even so).

Thinking the OS X 10.6.3 Installer would probably quit safely if it couldn't proceed for some reason, I upgraded in about 40 minutes, then updated to 10.6.8 (and Safari 5.0.5).

So far, so good. I don't much like the pop-up menus you get from the Dock icons - in Leopard 10.5.8, they were very simple and easy to use; now, in Snow Leopard 10.6.8 the screen dims, icons move, you have to navigate the cursor around a right angle - too complicated! Or does all this business serve a purpose?

But I run a widely-supported OS again, right? And Mac seems happier than before.