While ultimately very similar to the Naos Pro in terms of performance, the Castor Pro is in a better position by comparison. Much like the Naos Pro, the Castor Pro is hampered by comparably high weight and unreasonably high price. However, unlike the Naos Pro, the Castor Pro lacks a competitor with the exact same shape. Back when it first released, the Castor got a lot of attention, not just for its technical qualities, but also for its oddly comfortable right-handed ergonomic shape. To this day, this shape hasn't really been replicated, which puts the Castor Pro in a unique position.

To be sure, the Castor Pro has more going for it than just the shape. In terms of sensor performance, I really don't have anything to complain about. Due to the lack of smoothing, motion delay is low across the board, polling stable, and CPI deviation nonexistent. The great sensor performance is further complemented by the flexible cable and high-quality 100% PTFE feet. Compared to the Naos Pro, I've also found the buttons to be a bit more pleasing on this one. Once again outfitted with Kailh GM 8.0 switches, the main buttons provide firm and snappy feedback without being overly heavy, while the side buttons suffer from above average travel even though the clicks themselves are pleasing. Despite featuring an ALPS encoder, the scroll wheel isn't anything special, displaying decent tactility but fairly high noise levels. Furthermore, I've found how low the wheel sits a bit weird, though this surely is a matter of preference.

At 96 g, the Castor Pro thankfully isn't as heavy as the Naos Pro, but once again, saving weight clearly was no concern when conceiving this mouse. With some smart engineering, it would have been easy to shave off at least 10 if not 15 g without compromising build quality—which, admittedly, is very solid, but the same goes for a mouse such as the MM731, which weighs almost 40 g less while being wireless and similarly sized. Instead, all PCBs are incredibly thick for no good reason, lots of excessive plastic is used, and the shell itself is excessively thick as well, to where no gain in structural rigidity is achieved. A weight range of 80–85 g would have been more reasonable and interacted favorably with the cable and feet.

Originally, the Castor Pro suffered from excruciatingly high click latency, but thankfully, Mionix will address this in a similar fashion as on the Naos Pro. Accordingly, only two main criticisms remain: The aforementioned above average weight and the price. At $79.99, the Castor Pro costs more than even some top-tier wireless mice without providing anything special feature-wise. On the other hand, the shape still is special, and to this day, there isn't anything truly like it, which is why the Castor Pro could be a worthwhile option for those infatuated with the Castor shape, especially on a sale. For everyone else, there are better options.