Hmm. I think it depends, really, on what you consider Ambition. After all, a Sense of Adventure could be as much to generating new stories as Ambition. Even if your SO isn't storming the corporate ladder, it's possible he/she is the sort to drag you to varied and sundry New Things To Do (or the like).

This from a guy who's not particularly ambitious career-wise, but tries to do New Things nonetheless.