For me, the biggest fix was reporting. In Apple Remote Desktop 2, reports were never guaranteed to work right. Sometimes you'd get one report, but not another. Sometimes you'd get a report, but not be able to run it again. I was pleased to note that with Apple Remote Desktop 3, reports always work for me... every time.
Considering that gathering data on my client systems is an important part of my work, more reliable reporting is always a good thing. Along those lines, Apple added a couple of new reports that are of particular interest to the enterprise: User History and Application Usage activity reporting. The fact is, in our current, rather highly regulated environment, you need to be able to tell who was logged in where, (from where in some cases), and what they were using, for how long.
In Version 3, Apple Remote Desktop makes this a simple menu choice. The find-remote-files feature has been improved, and if your clients are using Spotlight, you can search for files via that search mechanism, as well. Moving files to and from a specific client can now be accomplished via drag-and-drop, ala Timbuktu and Virtual PC, a rather nice improvement over the old multi-step process in Version 2.
For those of us who don't like the idea of unencrypted connections on our network, (which should be all of us), Apple Remote Desktop adds more encryption options, so that copy, installation, and reporting tasks now can be encrypted. More encryption options are always good.
Apple also recognized that while available bandwidth in the enterprise is always rising, there are those of us who do not, in fact, want Apple Remote Desktop to use all the bandwidth all the time. That means added ability to limit bandwidth usage when copying files or installer packages.
When it comes to installing packages, Apple added a rather major new ability in Apple Remote Desktop 3 by integrating the Task Server into installation tasks. The Task Server is a second 'headless' installation of Apple Remote Desktop administrator that acts as a centralized 'store and forward' node for various Apple Remote Desktop operations. Prior to Version3, it was only usable for reporting. While that's a nice feature, it's not one that made a Task Server something you particularly needed.
By adding installations to the Task Server feature set, Apple has given administrators a more compelling reason to fork over the extra cash for another license of Apple Remote Desktop.
Now when you're going to push out a big installer package to a few hundred, or even a thousand client Macs, instead of having to sit at your administrator workstation and wait for that task to complete, you can foist it off on the task server. And that will include scheduling it to happen in the dark of night, without having to leave your copy of Apple Remote Desktop running. Very convenient, very nice.
Another rather huge feature for me is the addition of AppleScript abilities to the Apple Remote Desktop application itself.
While you could always run remote scripts on clients via Apple Remote Desktop, and that was nice, Apple Remote Desktop itself was not automatable prior to Version 3. Apple has fixed that problem, and I'm more than pleased. Of course, Apple is pushing this via Automator, its more friendly automation tool, but automation is a help far beyond that. Between a scriptable Apple Remote Desktop, and folder actions, or scripts that automatically run based on adding/removing items from a folder, I can do the same things I did with previous versions of Apple Remote Desktop, only with far fewer steps.
Now to install a package, I don't even need to go into Apple Remote Desktop at all. I just drop the package into the 'Install everywhere' folder, and AppleScript does the rest. If I need people to sign off, I don't have to make with the clicky, and send messages manually. I just write it once in a text file, and drop that file in the right folder. Bang, done.
There's some holes in this feature. You can't script reports, (a large oversight), and you can't automate preferences settings, (an annoyance), but it's a heck of a start.
There are some things Apple could do better. There always are.
I'd still like to see Apple Remote Desktop administrator ship as part of Mac OS X Server, at the very least on an Xserve. A public plug-in architecture would be great. It would enable others to add features that Apple doesn't have. For instance, Microsoft Remote Desktop support would help create a cottage industry around Apple Remote Desktop. Being able to point Apple Remote Desktop and/or a Task Server at more than just the built-in database would make integrating Apple Remote Desktop data with other management tool data easier.
I think making just the Task Server engine a standard part of Mac OS X Server is an idea worth looking into, as well. (That way, you get the Task Server out there and people are only paying for the Administrator UI).
There's no upgrade pricing, and for some, that's more than annoying. However, since Apple doesn't hit you with a per-client tax, no CALs, etc., $500 for as many clients as you can handle from a single workstation is definitely not a sharp stick in the eye, either. If you run Macs, (or anything, really) Apple Remote Desktop is a good tool to have, and well worth the cost.