I got a couple of samples a few months ago. I have a 1.1mm Standard Striker, and a 1.5mm XL Striker. I like the XL size better, but think I like the 1.1mm thickness better, but it looks like they don't come sized that way. I also think I'd like to try the Axis.
I ended up getting a Blue Chip pick, so I don't use the Gravity Picks much, but I do like them better than any of my other cheap picks. The ones I have are a little more clicky than I like for strumming, but are nice for flatpicking, and the surface is much grippier than most other cheap picks as well.
Definitely worth checking out.
Jason