A promotional image of the new "CrossHatch" infill. The image reads "Print Fast & Quiet, CrossHatch Infill, Much Faster than Gyroid Infill, Much Quieter than Grid Infill, Less Vibration & Nozzle Collision, No Line Intersection". There is then an image of 3 layers, the first and third are "Hatch" with the description "Aligned Rectilinear Infill (smooth + fast)." The middle layer is "Cross" with the description "Transition Layers for Periodical Direction Shift (directional transfer + strength)."
From: https://www.reddit.com/r/BambuLab/comments/1crq25n/introducing_crosshatch_infill/

Yesterday, Bambu Lab promoted on Reddit the new CrossHatch infill, added in Bambu Studio 1.9.1 Beta 4. In their release notes, Bambu Lab described CrossHatch infill like this:

We developed a new infill pattern called CrossHatch. As the name suggests, it primarily fills parts with lines, while periodically altering the direction of the lines through some transition layers. It dramatically improves strength compared to line and concentric infill, while achieving high speed and silent printing in most layers.

When compared to Gyroid infill, it prints 28% quicker in a test cube. When compared to Grid infill, it has a smaller grid size at the same density setting. Based on our tests, we recommend printing it with a slightly lower density setting than you normally would, such as 12%.

https://github.com/bambulab/BambuStudio/releases/tag/v01.09.01.58

Some people claim they have been testing it for some time now and it seems to hold its promises in terms of speed. Regardless of which group you are in when it comes to whether infill contributes to the strength of a print or not, it seems CrossHatch infill has not proven itself quite there yet.

In any case, feel free to share your experience with this new infill in the comments.