To be clear, their own proprietary channels, layers and masks right? You can't open a Photoshop created document with those elements and further edit an existing layer right? That's proprietary Adobe processing (meaning any other software you move to, you now hook into their proprietary processing).
The DP Review article didn't mention that as far as I could see. 10 Photo Editing Programs (that aren't Photoshop) also don't support Photoshop legacy data which is proprietary unless I'm missing something.
Actually, to a certain extent, adjustment layers in a PS document can be read and recreated by Photoline. For example, an adjustment layer stack with curves, hue/sat and levels adjustment layers created in PS and saved to a PSD file (PSCS6) will open in Photoline (v17.53) with all of those (supported, or analogous) PS adjustment layers intact and applied to the background image. There are some discrepancies - I noted that, for example, if I applied a gamma and white point levels adjustment to the RGB channel, it was interpreted correctly by Photoline; however, if, in that same levels adjustment layer I also applied a gamma and white point adjustment to the GREEN channel, that was not preserved by Photoline. Interesting. I will contact the developers and see if this is a "bug" or something intentional. I am guessing it is a bug, as the curves adjustment layer, per channel, is preserved as well as the hue/sat, per target color range, is preserved. I have not looked into the fidelity of the translation in terms of color numbers, etc.
Layer masks are also preserved although I am not sure if they are fully registered with the image. It appears that the layer masks created in PS are displaced or have their left bounding box margins justified to the left of the image space in PL. Maybe? - will need to experiment with this.
I assume that if PS has a layer adjustment that has no mate in Photoline, it probably will not be preserved. (EDIT - an unsupported adjustment layer comes in as a fully transparent layer with no mask in Photoline - for example, I applied a LUT adjustment layer with a painted mask to the PSD file in PSCS6 - upon opening in Photoline it was in the layer stack, but as a transparent layer, with no mask.
Anyway, pretty interesting.
EDIT - attached is a screenshot with the comparison. Although cyclocross races can be hellish, these adjustments were arbitrary and were made so that they were obvious.