Nice mouse, stylingwise at least.
Sadly though, ADNS-9800 is not as good as most customers think and most reviewers constantly make it out to be.
No optical sensor (and lasers are optical sensors, too, although common speech mostly suggests otherwise) responses completely linearly. ADNS-9800 deviates more from the optimum than ADNS-3090 with LED illumination, to a point, where it becomes perceptible to at least some users. It is being noticed as positive acceleration, which cannot be disabled either, since it is inherent to the hardware itself.
While this is a rather small issue, which will be overlooked by most and might be acceptable to others (although I do not consider it acceptable that there never was any attempt to remove it), it is not the sensor's only flaw.
In order to achieve stabile tracking up to the ridiculous dpi range of 8200, another algorithm is applied, to "smoothen" or "stabilize" (in absence of a better term) the cursor movement. This prevents the movement to become "jittery", which could be made visible via MS Paint and would cause erratic movement.
As it is being calculated via MCU, which happens after the physical movement data have been picked up by the sensor, this algorithm delays the process of transcription into cursor movement.
This delay also is noticeable for many users, which is why most companies provide a newer firmware version by now that is supposed to lower the levels the algorithm works on (you can look into that on Corsair's support forum for example, where in concerns users of M65 and M95)
Despite of that, it is still present - and it is still possible that some users might notice it, the cursor basically will stay a slight little bit behind the actual movement (beyond the normal value - of course, there is always system-based inputlag).
Therefore I advise everyone to thoroughly research mouse technology before buying a product using ANDS-9800. It was developed for enourmous dpi only (which basically just means a higher possible cursor speed, but still is very effective marketingwise) without putting linearity of tracking or any other aspect into account. Yes, most users won't be affected by it (or at least not notice being affected), still, if you need the extent of configurability a laser sensor offers or use the mouse at a really high sensitivity, on which LED-based optical sensors wouldn't be tracking effective anymore, I would suggest to buy a mouse with ADNS-9500. In any other case, a LED-based sensor might be the better option.
Otherwise a nicely written review, I like the style being applied by the author. Still, mouse technology is not being tested to an acceptable extent on all the internet. Hopefully this will change some day.