The romances are all covered at sorcerors.net. For a thread specifically about Viconia, try
here. Since you asked for spoilers...
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Basically, there is no point to romancing people in a videogame apart from fun. if you mean other major events in the romance, then yes there are. She gets attacked by some er hunters from the spider queen. (I forget what they're called =(. I'm not sure if you actually fight Haer'Dalis if you keep him and romanced Aerie in your group. I don't like Haer'Dalis so never tried it. However, extra experience should only apply with power gaming. If you wanna have fun, don't worry about experience. As long as you do a reasonable amount of sidequests, all fights in the game should be pretty easy. Unless, of course, you download a bunch of improved battles =)
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ToB Spoiler
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Viconia'll change alignment in ToB if you want.