About a minute ...

[lao tzu]

... until Lion is installed on my iMac.

[lao tzu]

On the iMac now ... first impressions:

Scrollbar looks different, and scrolling itself is reversed from previous orientation on my mouse wheel.
Launchpad is so obviously set for gestures ... no convenient way to move from one screen of apps to another without one.

On another note: I downloaded Lion when it became available last week, but the download was corrupted. The app store had no obvious method to download it again. I waited until today to see if the issue had been addressed in the community forums. It was:

• Exit App Store
• Exit Lion Installation (if it opens)
• Go to Applications folder
▪ Find and Delete the file named "Install Mac OS X Lion"
• Restart the Mac
• Open App Store
• Go to Purchases tab
• Click Install to redownload the OS X Lion
• If it shows as Installed:
▪ To redownload the installer, press and hold the Option key while you click the Purchases tab. If the button to the right of the Install Mac OS X Lion item doesn't change to "Install" and allow you to download Lion, use Spotlight to search for "Install Mac OS X Lion" on your computer.
That's it!

I can afford to guinea pig the iMac for trouble-shooting, but I'm holding off on my MacBook Air because of all the third-party software I use, that I can't afford to be without.

[lao tzu]

On the first restart, my desktop icons were scattered across the screen. I think this is because I use a low screen resolution to make it easier to see the screen from 6 feet away. (I typically use this machine while it's sitting on the table at my feet and I'm reclined on my couch.)

Software update ran on its own when Lion installed, and tried to load up java runtime, but again, the download was corrupted. After doing a cold reboot, software update ran again, and this time installed without a hitch.

After the cold reboot, the apps that had been previously running restored to exactly where they'd been. This is an interesting feature. It brought my browser, for instance, right back to this page, with this tab selected.

[lao tzu]

no convenient way to move from one screen of apps to another without one.

Okay, this one is resolved. Click the screen, anywhere there's not an app, and drag it left or right. Moving apps around is intuitive. Just grab and place. I've created a screen of most used apps.

[lao tzu]

scrolling itself is reversed from previous orientation on my mouse wheel

This is a checkbox option on the Mouse system settings, right up top: Move content in the direction of finger movement when scrolling. Deselecting brings the scroll orientation back to what I'm used to.

[lao tzu]

FileVault has changed. I've selected to turn off the legacy filevault in order to upgrade. This is not a quick action ... about 8 hours to complete the process, so I'm back on the Air for the interim.