My next playthrough - Miya Soral, Mephistopheles Tiefling wizard - I like the Faust story (both from Goethe and the medieval story), so I wanted of course my Tiefling be a from the Mephistopheles line. I might try the Astarion romance with her, even though I'm not a fan of that companion. But he has a lot of fans, so I thought, I see, what all the fuss is about.
You should always check the health of any potential partner's teeth before getting involved with them, and Astarion's mouth is in excellent shape for a 200+ year old dude. Excellent choice.