This is an extremely short article as there is just so much to explore with mantle. It will remains to bee very simple though. On high-end PCs with a single graphics card you may see perf increase in the 10% area. On massively CPU limited situations like low/medium quality settings / low resolutions or even Multi-GPU setup, that's where the gain easily can get 30 even 40%. As such Mantle will benefit low-end and mainstream processor based PCs the most. But even at Enthusiast class, it will make a difference.
Bon c'est plutôt encourageant, si je gagne 10-15% sur I5/7970 ca sera bien.