This game is brilliant. And it gets really, really good. The addition of modding is fantastic. I just need to make a few remarks on the modding idea.
1) Modding idea is fantastic, but it can create large problems for future versions if not carefully designed.
2) Really good modding must have a very well organized structure, documentation and functionality (one external robust tool to create mods is a good start).
3) Modding is really fun until everyone decides to make their own external tool to create mods (this creates chaos and problems for future mod developers).
4) Modding distribution and creation must have from the beginning a simple dedicated web page (here you have everything - how to make mods , sharing mods, mods library).
5) Modding should include clear and robust API used by all modders (this is hard and complex to handle but it is essential).
6) Making mods should be easy to get into and hard for changing gameplay feeling.
This remarks are based on years of observing, playing and modding Minecraft. I would also like to thanks to all the people who put a lot of time in making this amazing game !