DesktopX is about being able to take your Windows desktop and add stuff beyond icons. And it does this by letting you add objects to the Windows desktop. What is done with those objects, depends on the user. You can take those objects and put them together and build an entirely new desktop. Or you could put them together into a mini-application and export them as a widget.
Widgets have become pretty popular because they take up less memory than a normal program but can do the same kinds of things as a program. And enough time has passed that a few common widgets have emerged -- clocks, calendars, weather monitors, stock tickers, MP3 players, etc.
In most "widget" enabling programs, all widgets are created in a scripting language (JavaScript or VB Script typically). This is good but it does require that the person making the widget be reasonably technically knowledgeable.
But if we know what kinds of widgets people are making, can we not make it a bit easier? That's where the "Additional Abilities" feature of DesktopX come in. Additional abilities come in the form of plugins. Plugins take care of most of the work for the widget developer and typically provide a GUI configuration to allow developers to determine the specific functionality of their objects without coding.
One plugin that has been heavily revamped for DesktopX 3 is DXPlayer. DXPlayer was designed to make it much easier to create media players with DesktopX. In fact, it is easier to create really slick looking MP3 players with DesktopX than it is to create them using Winamp 5 (modern) or Windows Media Player.
Let's take a look at just how easy that is.

The first step is to create a DesktopX object.

Now we need to give our object an image. This is just a matter of getting a PNG file. So here's a play PNG image.

For my "play" button I want to have a mouse down state. No problem, very easy.

Next, I want to create my other objects. To save time, I'll right click on my play button object and clone it a few times and assign them images.

So here's where we're at. I've got a background image and 3 buttons. Next I'll create the track name text.

So I create the object, go to the states tab, on appearance I make it a "text" object. Then I change its color to be white.

Now it's time to start making these buttons and things to something. So I go back to the general tab on each object, press the "add button" and pick the "DXPlayer" plugin.

Now I select it and press "Configure". The first button I choose play, the next one I choose "pause/resume" and the last button I choose "Next".

For the text, I don't want it to be a button but rather a text display so I choose that from the combo box and then choose "track name".

Now I group them together.

And finally export it as a widget.

The DXPlayer plugin already supports Winamp, iTunes, CoolPlayer, ObjectMedia, or an Internal player which requires no external media player at all but rather works with the OS directly. It typically makes sense to let DXPlayer choose what to use so that other people will be able to easily use it with whatever their media player of choice is. But obviously if you want it to be stand-alone you'll want it to be internal.
Now obviously this is a very simple player. There are MP3 players with play lists, equalizers, album pictures, animations, etc. But you get the idea.
Here's my final widget, total time taken (including taking screenshots): ~ 3 minutes.

The ability for developers to pick between plugins (or even make their own plugins) or do it in script is one of the major advantages of using DesktopX. Over time, hopefully third party developers will create plugins (the plugin development guide can be found here). But Stardock plans to create more as well over time. There's plugins for creating resource meters of various kinds, clocks (one reason we have so many clocks, and several other kinds).
Have fun!