Metadot claims the Das Keyboard 4 is an "order-of-magnitude improvement over past generation Das Keyboards," which is something we're qualified to offer an opinion on. Among the many mechanical keyboards we've used over the years, previous generation Das Keyboards have been among them.
The shape of the Das Keyboard 4 is similar to its predecessor, but the glossy faceplate is gone; it's been traded in for an anodized aluminum top panel that's obviously not as shiny, though still sleek and attractive, far less prone to finger smudges, and intended to improve durability. Astute observers will also notice a new font, at least for the Professional version with laser-etched key caps. Metadot says it changed the font to make the keys easier to read, but didn't go crazy with a funky font that draws unnecessary attention. We're rather indifferent to the font type and more interested to see if the laser-etchings resist fading over time as promised.
Metadot's changes aren't only skin deep. The Das Keyboard 4 sports sports a "refined" enclosure to eliminate vibration, along with hex screws for no particular reason we're aware of. We don't typically curse the awful vibrations that apparently plague keyboards, but we can say the Das Keyboard 4 is a solid plank that should have no trouble withstanding power typists who may come down harder on key presses than the average Joe. It's also a heavy keyboard at 2.9 pounds.
At long last, media controls! They're somewhat limited compared to keyboards that offer dual-Function keys, but you do get dedicated rewind, fast forward, play/pause, and mute buttons, along with a sleep button and an oversized volume knob reminiscent of a HiFi stereo system.
Metadot also upgraded the built-in USB hub to SuperSpeed USB 3.0. The two ports sit on the top-right of the keyboard just above the logo.
Is that a detachable ruler on the backside of the Das Keyboard 4? Why yes, it is. The ruler is magnetically attached for easy removal, though the obvious question is why the frack did Metadot include one in the first place? Metadot's answer is, "Why not" with a promise that "you'll thank us later." Admittedly, there are times when access to a ruler comes in handy, such as measuring the dimensions of a shipping box after having sold something on eBay. Still, it's an unlikely (and quirky) combination.
Beyond being able to make measurements, the ruler also serves as a makeshift footbar that raises and angles the Das Keyboard up slightly.