GLX-Dock 2.2 is designed to be less obtrusive on the desktop by introducing two new visibility modes: to hide the dock when it overlaps an active window or to hide the dock when it overlays any window (whether it's active or not). This new beta version of GLX-Dock is designed to be more useful by adding the ability to manage tasks within the clock applet's calendar, to lock the screen with the log-out applet, to create tiny URLs using a drop-and-share applet, and making other applet improvements. The D-Bus API has also been extended for greater functionality within applets.
In terms of being GLX-Dock 2.2 being simple, all of the GLX-Dock themes have been polished and the simple configuration panel now allows for quicker and easier customization (the developers say it can be configured within five minutes). GLX-Dock now also offers up a Unity theme based upon Canonical's recent Unity Desktop work with Ubuntu. With this Unity work and to make GLX-Dock work better for netbooks, there's now the ability to spread application icons across multiple docks (as many as you want) and each of the docks can be configured independently.
The release announcement for GLX-Dock 2.2 Beta can be found on the Launchpad announcement page.