Well, Plutarch has this to say about her looks:
"For her beauty, as we are told, was in itself not altogether incomparable, nor such as to strike those who saw her; but converse with her had an irresistible charm, and her presence, combined with the persuasiveness of her discourse and the character which was somehow diffused about her behaviour towards others, had something stimulating about it. There was sweetness also in the tones of her voice; and her tongue, like an instrument of many strings, she could readily turn to whatever language she pleased..."
-Life of Antony (XXVII.2-3)
Saying her beauty wasn't incomparable is a backhanded insult to be sure but not exactly a devastating critique of her looks. Beauty ideals change over time, too, so it's entirely possible she looks better to our modern eyes than she did to her contemporaries.
