You can hold ⌥ (Option) to make windows resize symmetrically, from the center. It even works when resizing from any corner in Lion. Update: You can also hold ⇧ (Shift) to resize a window proportionally.

As far as I can tell this is brand new in Lion, the first version of OS X that allowed resizing windows from any side.

You open up the PSD in Preview, make a minor edit to it such as adding a little text to it or draw a couple of red lines. The intention is to select all, copy, and go to your email app to paste it into a message. You'll just undo the changes or close it without saving later on.

In the background, when you left Preview it autosaved the file and destroyed all the layers. You even quit Preview without thinking, so you didn't get a chance to decline saving it.

Now, you could then reopen the image in Preview and use the "Revert Document…" menu or you could use Time Machine to get an older version back, but wow that's annoying.

On Lion only, to make recent backups available to Time Machine users while travelling or otherwise away from their backups, Time Machine may make "Local Snapshots" hourly.
These snapshots are made only on portable Macs, and are kept on the Mac's internal HD (and on any other disks/partitions being backed-up) for a few days, space permitting.

Don’t buy Apple’s $69 OS X Lion USB Thumb Drive. The Apple Store webpage for the Lion USB Thumb Drive states: “When you install OS X Lion using the USB thumb drive, you will not be able to reinstall OS X Lion from Lion Recovery. You will need to use the USB thumb drive to reinstall OS X Lion.”

The reason for this limitation is that Recovery HD, before allowing you to reinstall Lion, checks with Apple’s servers to verify your computer’s eligibility. Unless you purchased Lion from the Mac App Store, the verification will fail.

What if you want both an Internet-free Install Lion thumb drive and the ability to use Recovery HD to reinstall Lion? Apple’s “official” solution is to purchase Lion from the Mac App Store ($29) and buy a Lion USB Thumb Drive. This will cost you $69 + $29 = $98.

But there is a far cheaper solution. Buy the Mac App Store version of Lion and make your own 5GB or larger USB Install Lion thumb drive, using a simple procedure detailed on numerous web pages (such as this Macworld article by Dan Frakes). Assuming your thumb drive costs $10, your final cost is $39 — saving you $59 over Apple’s official route.

I would like to call for a place to list some little things that surprise you about Lion. There are so many articles and lists of all the new features with information overload, I would rather focus this spot of the site on tiny delights with a note why it makes a difference to you.

Please one topic per answer, this isn't a race to enumerate everything that changed. This isn't the place for massive topics like the implications of FileVault 2 on your entire workflow - just a stroll past some little gems, fun oddities or subtle changes specific to Lion.

While Time Machine gained a couple new features in Lion, I've just stumbled across one (so far as I know, undocumented) new piece of functionality in Apple's backup software that will have a lot of users cheering: You can now use a previous Time Machine disk with a new computer and inherit the entire backup history of the older machine. And it doesn't even require a flux capacitor.

OS X Lion is now available from the Mac App Store and we know that many of you are preparing or have already started downloading and installing the new cat.

Because installation takes place entirely from within the Mac App Store, the usual “clean install” option isn’t present. If you’ve followed our guide for preparing your Mac for Lion, you’re probably in good shape to proceed with an upgrade. If, however, you long for the ability to do a clean install without having to first install Snow Leopard and THEN install Lion, Mashable has you covered.

If you want to create a bootable USB stick or burn a DVD of OS X Lion, read along.