So I've played with these for two months, when I started learning guitar. Since I want to play hard rock, I imagined these would be perfect for me. They really do give me great sound, fat and heavy rock sound.
However since I'm a total beginner, picking with these, especially fast strumming, can be a bit tricky. If you haven't got your strumming tehnique perfected, the pick can get stuck between the strings since it's very stiff. This is just a matter of practise though.
One flaw this pick can have is its grip. If your hands get too sweaty when playing, I'm afraid this pick is a poor choice for you. Except for that, its grip is not exactly terrible, but it definitely hasn't got the greatest grip.
The durability doesn't seem to be a problem so far. My picks show some marks of wearing off, but I pick and strum very hard too, so I can't expect them to look as new.
So if you want to play some hard rock, it can't hurt to try these out. I'll probably check out some other picks next, but I'd happily come back to these if I can't find anything else.