Overall performance is much improved. Quartz Extreme is the marketing term for unloading the video tasks to the video card. Most of us are used to the concept in gaming where newer faster video cards are a way of life for making the games playable. What Nvidia does for gaming, Jaguar does for exverything else. Of course, the card you actually have in your machine makes a difference, but I'm delighted to report that a 500mhz tiBook, with its 16 meg card sees a marked improvement, system wide, in performance.
Sherlock is not the 'find' interface anymore. You might think this is a bad thing, but I deplore having to open an application to simply find a file. Command-f (at least in the build I'm using) maps to a simple Finder window with a search interface. Key strokes are not lost as the window opens like they are when Sherlock is opening. So, command-f, start typing and hit return makes for a super fast way to find a file.
Sherlock 3 is pretty cool. But so is Watson, which deserves credit for being ahead of the curve.
The Sharing control panel includes a firewall interface. I consider myself to be a Mac power user who is comfortable with a command line. But, having an ultra simple and straight forward Firewall interface is awesome.
Command-tab is more of a toggle now. It used to be that command-tab'ing would always step you thru the open applications in a linear fashion. BBEdit munkies like myself would have to command-tab-tab-tab, etc until you go to the browser, and do it again to get back to BBEdit. Now, if you command-tab, it selects the app you were in last before stepping forward. This means fewer keystrokes.