You communicate really well with each other, perhaps better than with anyone else you've ever been romantically involved with. You are ultra-aware from the start of what each other's needs are within the relationship, and you know just where you stand with each other. Where other relationships are hindered by bad communication and mixed messages, yours is a model of clarity and directness!
But it won't even be solely due to overt verbal communication, though you, especially, are good at that, too. You just have a wonderfully strong mental connection that allows you to tune right in to each other, like tuning in to a strong radio frequency. But talking is a solid bond between you as well, and you love discussing everything that comes up, from the insignificant thoughts that just flit into your consciousness to the heavier, more important concepts that you're each grappling with in your lives. Ideas are an important part of your relationship -- communicating your own ideas to each other and helping each other hone those ideas, come up with newer and better ones and generally broaden your horizons. Though this aspect is a mental one first and foremost, it influences the more emotional side of your connection in that it fosters such a feeling of understanding and accessibility between you. But the mental side of things will have to be firmly in place before either of you will want to take things further, and this aspect will help with that.