Thanks to duathlon racing events, a nordic discipline presently more popular in Europe than the United States, there is now a combination boot that uses the Salomon Pilot binding for skating, but attaches to the Profil flexor-type binding for classical.
The weakness of combi boots has always been that they needed flexibility under the ball of the foot to allow classical striding, but that flexibility seriously reduced their lateral stiffness for skating. Salomon's new Carbon Pro Skiathlon takes advantage of the fact that Pilot boots have always been able to snap into Profil bindings. The carbon sole plate gives springy flexibility to the forefoot, while the double-bar Pilot binding retains a large amount of control in skating.
Like any combi boot, it does not do each tehnique as well as the boots specifically designed for them, but it does them much better than any previous version.
The boots aren't cheap. As part of the Carbon Pro series, they retail around $350 US. But specific skate and classic boots would end up costing at least $500.
The performance of the boot depends on the carbon sole plate. The carbon layer provides strength and flexibility with less weight and bulk than the plastics used in the Race Skate 9 and Race Classic 9. The 9s are great boots. They provide excellent fit and performance, and some different fit options for different-shaped feet. But they aren't as light as the boots in the Carbon series. The flexible carbon sole of the Skiathlon will retain its performance better than any previous version of combi boot. If you really want to use one boot for both techniques, the best you can do right now is the Skiathlon.
A couple of testers have said they like the support of the taller boot on long descents, especially when they are getting tired.
Most testers have rated its skating performance as merely adequate, but that's reasonable when they're coming from dedicated skate boots. The Skiathlon has a softer cuff and looser ankle strap, adaptations for classical skiing, as well as a forefoot very similar to the Carbon Classic. If you haven't skied a Pilot boot before, you may feel the performance is a significant step up from your previous boot.