The Naos 5000 is a brilliant alternative to the SteelSeries Xai for those that want a similar performing right hand only mouse. The performance of the mouse as a complete package is definitely on par with that of the SteelSeries mouse, however, the Naos has an issue with a slight wobble which does not necessarily degrade performance much, but is annoying. Even though it might fix itself over time as the mouse feet get worn down, a € 70 mouse should not have these kinds of problems and therefore this mouse cannot achieve a high score.
If you want one of the best sensors around in a well executed package (besides the wobble), then the Naos 5000 should definitely be on your short list. While it is less expensive than the SteelSeries equivalent it is still a very expensive piece of kit that not every mouse user needs.