Hazel 3 also includes a miscellany of fixes. For example, the app should now behave better when it's dealing with external drives: If a rule fails because the destination drive is unavailable, Hazel won't keep retrying over and over; it will instead wait until the drive comes online, then run the action. (For example, my Time Machine drive occasionally decides to stop working; I've long had a Hazel rule that keeps an eye on the drive and, if it hasn't changed in the past 24 hours, gives me a Growl alert. In Hazel 3, when I take my laptop home, that rule is suspended until I'm back in the office.)
Noodlesoft's change log lists more than fifty other tweaks and fixes since I reviewed Hazel 2.3. But those updates don't change the essential nature of the app--they just make it better. As with version 2, Hazel 3 sometimes requires some trial and error before it'll do what you want. (Tip: you don't have to do everything in one rule; a lot of the time, it's easier to set up a series of rules.) And learning to work with files in multiple levels of subfolders is tricky. But if you invest the up-front time Hazel sometimes demands, you'll get a neater, better organized drive with little to no further effort.