RE: the dating a therapist/psych person vs. someone outside that realm, it's probably just going to come down to personal preference. I've dated clinical psych, experimental psych, and completely unrelated to psych, and had great times with all of the above. With clinical folks, obviously there are lots of conversations about general psych/clinical-related topics, but I personally found that to be really interesting; I should say, though, that these were people in different specialties than myself. With the experimental folks, if we "talked shop," it was usually more research-oriented, which again was very interesting. And with the non-psych folks, if I talked about work, it was in part to explain what I did and what sorts of stuff I saw everyday (and vice-versa for them).
For me, I've typically enjoyed dating someone who's psych-oriented (or, as WisNeuro said, med-oriented) more so than someone in a completely different field, in part because there's always been an inherent understanding about when we want to talk about work and when we just need to shut that down and focus on something else. But that's just me, and that might've been more a factor of the individual people rather than their professions.