Honestly, I don't care so much about him staying in Europe as I do him going full-time.
In terms of the work, yes, he's done most of the programming to date. I've worked with him to design the actual product and had the vision of the core functionality, but yes, he's done the hard part of coding it and what not.
Also, the lead investor we're talking to (who is awesome and an active entrepreneur in our space) currently is an exec in company that has a dev team on the other side of the ocean. Based on his ongoing experience, he thinks the distributed team model sucks and wants our CTO to be here in the US alongside the dev team. I tend to agree with him, as my cofounder and I have had WAY more productive, creative conversation when he was here vs via Skype.
Honestly, if he was willing to give me a firm answer in terms of "when we raise x amt of money, then I'll go full-time," then i'd have no problem. But right now he's being totally vague, and doesn't seem willing to commit to anything specific.
Also, more generally, we've built something very cool, but our product isn't too hard to imitate/copy at this point. We need to kind of sprint to get to the point where network effects kick in, etc. This is also a source of frustration.