4 port USB 2.0 hub
Note that the USB provider is a hub - a few people have reported some USB peripherals (such as Palms) having problems due to it being a hub, although the majority of people do not have this problem, and the usefulness of the 4 port hub outweighs any potential downside. If you encounter problems, you can always use the USB ports on your Thinkpad to get a direct connection.
LCD monitors are getting larger and higher-resolution. Currently, DVI based on 165MHz TDMS transmitters can only (officially) support 1600x1200x32 at 60Hz, which is the resolution of your average 20" non-widescreen LCD. IBM's driver support for this resolution through DVI ports on docks has been inconsistent. Also in Linux you might experience problems even with this resolution and IBM officially states that the pass-through DVI port only supports resolutions up to 1280x1024. Read our page of information on how to solve these troubles.
Please be aware that not all Thinkpad models will support DVI output with a Dock. Apparently, all X and T models from the 20 series do not. Please add other models if you know about them to not support DVI.