This is an interesting development from Sako. For a while, it looked as if the M100 was going to be the successor to the 85, but this 90 appears to be that successor. It is really an improved (in some ways) 85. The dual plunger ejectors would appear to be in response to the ejection problems some were having with their 85s. Structurally, the bolt and receiver are pretty much the same as on the 85, although Sako appears to have abandoned the "controlled round" feature claimed for the 85 (which was a real stretch), as the rim on the bottom of the bolt face of the 90 is not removed as it is on the 85, making the 90 clearly a push-feed action.
One big difference appears to be in the scope-mounting options, with the elimination of the time-honored tapered dovetail receiver top. We now have a choice of either (a) an integral Picatinny rail (which will appeal to a lot of shooters as it allows for a wide variety of scope rings to be used, not just those developed for the Sako dovetail) or (b) what Sako calls the "Sako 90 Optilock interface" which consists of a straight (not tapered) 17 mm dovetail with recoil slots at the rear of both dovetails. I'm guessing that Sako will produce mounts specifically for this option.
One thing that caught my eye in the technical discussion of the trigger is the lock time cited for the 90: < 1.3 ms., which is very fast. I don't know whether this is faster than the lock time of the 85, but it is much faster than that of most modern commercial bolt actions. In contrast, lock times for the Remington 700 and Post-64 Winchester M70 are 3.0 ms. (close to the 2.9 ms. of the Sako L461), and for the Ruger M77 and Weatherby Mk. V, 3.6 ms.. Fast lock time isn’t really of great importance in the hunting context, but definitely is in target shooting. The new trigger on the 90 looks very good, allowing some adjustments for length of pull and five weight-of-pull settings accessible without removal of the action from the stock.
One feature on the 90 that I'm wondering about is the recoil lug arrangement. It's really a "Rube Goldberg" setup on the 85. It would be great if Sako has gone to an integral recoil lug with the 90, but that might be asking too much.