Minecraft games at over 17.5 million at least.
Pocket Edition is missing a lot of what's included in the XBLA and PC versions, which is of course not surprising given the platforms. Nonetheless, one of the biggest and most asked-for absentees is online multiplayer - users can play together via local Wi-Fi, but not through the Internet. According to Bernhardsson, online multiplayer is now in the works.
It won't however feature in the next update, which would be 0.5.1. That's being targeted for late January/early February and mostly features "behind the scenes" fixes and tweaks.