Feature-rich is an appropriate term for the Astro C40. To start, it can operate both wirelessly via the included USB dongle and over a wired USB connection. The set-up process is a cinch regardless of platform or which connection you opt for: just plug in the USB cable or USB dongle, turn on the controller and you're ready to go.
If you prefer a set of headphones or a gaming headset over speakers, you'll be glad to know the C40 includes a standard 3.5mm headphone jack on its underside. It'll output game and chat audio as well as pass through your own chat audio from a headset microphone.
Like the Dualshock 4, the Astro C40 features a built-in speaker for the few games that take advantage of it. However, the C40 expands its functionality, using it to play a tone when the battery gets low so you know it's time to recharge.
It's also worth mentioning that the C40 supports gyro controls, just like the Dualshock 4. Some third-party PS4 controllers don't offer this feature, which can lead to issues in certain sections of games that rely on motion controls. With the C40, this isn't a concern.

Customisation is at the heart of the C40. Using the included tool, you can remove part of the controller's faceplate and swap around the D pad and analog sticks. This lets you switch between the parallel stick layout common to PlayStation controllers and the offset layout you find on Xbox and Nintendo controllers.
Along with adjusting the stick layout, you can change out the stick caps for a different feel and grip profile. The C40 comes with a few different types: two concave caps with small bumps for added grip, two convex caps with a rubber texture similar to the Dualshock 3 from the PS3 era, plus a variant of each with a taller shaft for folks who prefer more manoeuvrability in their sticks.
FPS fans can eke even more out of the triggers with the C40's trigger stops. These toggles let you reduce the throw distance of each trigger, making it so you only need to push down roughly half as far to achieve the same effect. This can be useful in first- and third-person shooters by reducing the time it takes for a full pull-and-release of the triggers, allowing for faster firing of semi-automatic weapons and less finger fatigue over the course of a gaming session.
The C40's rear buttons expand its versatility even further. By default, the right button is mapped to X (cross) and the left to O (circle), but they can be remapped to other buttons on-the-fly – you don't need to boot up the PC configuration software at all. You just hold down a small button on the back of the controller to activate mapping mode, press the rear button you want to map, then press the button you want to map it to. It's pleasantly simple.
This isn't limited to the rear buttons, either. Any button on the controller excluding the Option, Share and Home buttons can be remapped using the same process.
The Astro C40 configuration software builds upon the controller's core versatility with a simple interface for mapping all buttons and syncing the changes back to the controller. You can create multiple profiles with different mappings, two of which can be stored on the controller at any one time. A toggle on top of the controller lets you switch between those profiles on the fly.
The configuration software also lets you define the sensitivity curve of the sticks, adjusting the rate at which physical movement of the sticks translates to digital input. If you want the slightest nudge to send your character sprinting, for instance, you can do just that. There are similar sensitivity options for the rear triggers, too.
An unexpected feature of the C40 is its emphasis on audio quality. Whether you're connected wirelessly or over USB, the audio piping through the headphone jack outputs at 24-bit/48KHz, and the configuration software includes an equaliser if you want to tweak the balance of highs, lows and mids. You can adjust the microphone and built-in speaker volume, too, as well as how much of your own chat audio you hear back through the headphones.
Rounding out the configuration options are settings for the intensity of the rumble motors in either side of the controller, as well as the brightness level of the central LED.
For folks looking to the future and the launch of the PS5, the latest comments from Astro representatives (at the time of publishing this review) state "we have no compatibility statements to make regarding the PS5, but we are continuing to look into this for both the C40 TR Controller and the audio products such as our MixAmp Pro TR".