I was all prepared to get a Z2 to replace my factory Nav in my H3, but I keep hearing about all these problems with freezing, etc

Should I just go with a D3 and deal with the smaller screen?

The 1 disk slot really does not bother me much. Would I be loosing anything else?

You will also be losing the ability to store CDs on the HD, voice recognition, and dual zone capability. If that doesn't bother you, D3 is the best choice, and gives you better ipod interface