Inspired by your interesting review I gave PhotoFiltre a try and I agree with you on the very pleasant speed of this application and its ease of use.
However, it has been mentioned in several times in this thread that Photofiltre would be somehow equivalent to the likes of PaintShopPro. I disagree here because several very important tools are still missing from PF Studio 9. For example white balance, tone curves and a denoising tool seem to be missing. The tone adjustments are restricted to gamma and levels (under a misleading name) and "more shadows" "more highlights" commands. The sharpening options are also very reduced (sharpen, sharpen more) with the reinforce tool (likely an USM version) producing not so impressive results.
Somehow there seem to be some masking options implemented but there seems to be no straightforward way to use them as masking layers.
My impression is that the best argument for photofiltre is indeed speed and user friendliness as long as one wants to restrict oneself to comparatively simple editing operations. A comparison with PaintShop Pro, Photoline 32 or PhotoImpact is still a bit far fetched. It compares well with the free Paint.Net because of plugin support and speed, but Paint.net seems to develop faster.