After releasing a video of an early success, which seemed to work only in conjunction with some kind of hardware hacking, it's no surprise that Acekard Team is the first to reach this milestone. We have no idea how the 2i differs from previous flash carts -- it may be a new hardware revision or it may even be custom firmware! The point is that it works, at least until Nintendo releases the eventual update for the DSi firmware.
The Acekard 2i has yet to be stocked in any of the listed resellers, but that may be because it was just announced. Acekard Team promises that the new card "will come up in a very short time." You can see the Acekard 2i in action in this video, which does unfortunately include footage of swashbuckling-related activities.
See also: DSi hacked already?