Build QualityOverall build quality is very solid. When shaking or tapping the mouse, there is no rattle coming from the mouse itself. The door to the USB dongle compartment, however, doesn't sit completely tight and can make some noise when shaking the mouse violently. When applying lateral pressure, no creaking or flexing of the shell can be observed. Lastly, when slamming the mouse down, no accidental clicks occur.
The main buttons of the Razer Viper Ultimate are very good. The click feel is slightly subdued and not as snappy as with traditional mechanical switches, but the very low pre-travel and low post-travel result in a satisfying button experience nonetheless. They're fairly light clicks, but not as light as (e.g.) Logitech clicks. Razer Optical switches are used for the main buttons.
Side buttons are excellent. Pre-travel is very low and post-travel pretty much nonexistent. The side buttons on both sides are recessed to where they're almost flush with the shell. Although this does make it difficult to actuate them by just rolling one's thumb over them, it's a conscious design choice to make accidental actuation less likely, which is reasonable considering the Viper Ultimate is a truly ambidextrous mouse with side buttons on both sides. As for their placement and size, the side buttons sit right above the grip area and are medium-sized, which is the correct design choice for a low-profile mouse like the Viper Ultimate. I'm unable to recognize the brand of the switches used for the side buttons (logo looks like "Cf" or "CCf").
On the bottom of the mouse is a single button for cycling through the set CPI levels, as well as a simple on/off-switch.
The scroll wheel is very good. It's a bit noisy when scrolling down, but the steps are tactile and well-defined. The scroll wheel also has some nice texture on it which provides additional grip. No accidental scrolls happened during my testing. The middle (scroll wheel) click requires fairly little force for actuation. The encoder is a mechanical one from Kailh. I'm unable to identify the brand of the wheel click switch.
CoatingThe top of the Viper Ultimate is covered in a matte coating. It's nicely textured, very grippy, and doesn't attract fingerprints, dirt and the likes too much. It's easy to clean, and there are no signs of wear left after doing so. The sides are whole pieces of hardened rubber with a fine texture on them. They provide excellent grip, but do pick up dirt rather easily. As for their durability, I'm unable to tell at this point in time.
Button Sound Test
Getting the Viper Ultimate open is both difficult and easy. Removing the feet without destroying them in the process is rather difficult as they're perfectly fitted to the shell. I'd recommend heating them up beforehand and then gently pushing them into a direction with a fingernail in order to create a gap that provides some leverage at least. However, once the four main feet have been successfully removed, only four underlying screws need to be unscrewed and two hooks (one on each side) released to get the mouse open. The screws are Torx T6, so unless you have a T6 or TR6 screwdriver at your disposal, you're (both literally and figuratively) screwed. For releasing the hooks I'd recommend wedging in a credit card and gently pushing the top shell up.
The internal design is rather simple and—in my opinion—as good as it can be. Everything but the side buttons sits on the main PCB, while the side buttons have their own PCB which is screwed into the top shell and secures the internal battery (a 450 mAh Lithium Polymer battery). The battery being placed right in the middle ensures the weight distribution is optimal. Both PCBs are reasonably thin, which gives reason to believe that some thought has been put into the design to keep weight as low as possible. Irritatingly, the main PCB is held by only two screws despite another unused screw hole on the left side. Since the sensor lens rattle test didn't show any issues, I assume the main PCB is secured to a sufficient degree. The PCB has a "19 36" marking, which means that its production date was the first week of September. There's also the Razer-internal name for the Viper Ultimate on the PCB, "AVA T1."
The MCU is the nRF52840 from Nordic Semiconductor. Its datasheet can be found here. On the MCU itself it reads: N52840 QIAAC0 1903GE.
As for the soldering and general quality of the PCB, I was unable to find any noteworthy flaws.