Hazel 3 also provides better tools for matching patterns, so it can, say, watch for files whose names consist of three letters followed by three numbers. And the new version adds a Current Time condition, so you can (finally) have Hazel run a rule at a particular time--for example, If Current Time is 5:00 p.m., then do this.
The new Hazel also lets you do some nifty new things to matched files and folders. There's now an Import Into Aperture action, as well as a Sync action that synchronizes a file or folder--in one direction--with another location. The Sort Into Subfolders action now includes options for deleting, renaming, or replacing duplicates; and the Open and Reveal actions now give you the option to make the associated application or the Finder the frontmost window.
One of my favorite new features in the Actions section is that if you're renaming a selected file (or adding a comment to it), you can build the replacement text using tokens, similar to the ones Finder and Mail searches use to represent particular attributes--for example, filename and sequential numbers. Those tokens are easy to drag around and rearrange, making it easier to create the text you want. They're also intelligent--if you add the Name token, for example, you can opt to change the case of the text while you're at it. You can also use AppleScript to create custom tokens of your own.
As before, Hazel also includes some tools for managing your Trash: You can force the Trash to delete items that have been in the Trash for a specified period of time, or whenever the Trash reaches a certain size. And Hazel still has its AppSweep tool which, when you delete an app, finds support files that you might want to get rid of, too.
Noodlesoft has made some nice tweaks to the program's interface in version 3. You can now reorder conditions and actions up and down in the list by dragging them. (Execution order is often really important.) You can still preview folders, to see which files and folders within them will be acted on by which rules, but now that preview tool gets its own button, making it much easier to access. If you hover the cursor over a given file or folder in that preview window, a popover appears showing you which of that file's or folder's attributes match your rules. That said, there are still some minor interface bugs here and there, such as buttons that disappear when windows expand.