Nick and Jessica seem to have married for the long haul. I doubt they'll split up. You're only seeing what the cameras let you see anyways.
My sister and I both like Ashlee now...we're 28 and 30 respectively. I do think that Ashlee has a good voice, I like her album, and she is pretty. She is a different kind of pretty from Jessica, but I'd say that she's no less pretty. If she did something different with her hair, she'd be more conventionally pretty IMHO.