In some shuls - the men and women can see each other clearly, either because the mechitza is low or transparent or both. On other shuls - the men and women can't see each other. In other shuls, the women can see the men but the men can't see the women.
Now I understand the women being able to see the men. The main "action" is happening on that side and anyway, women [generally] don't get aroused seeing men swaying in their talleisim. But the notion of building a shul where the men can easily see the women davening strikes me as problematic. The Rambam writes in his פירוש המשניות that the women in the Beis Hamikdash stood in the balcony [the source for mechitzos in shul]
"כדי שלא יסתכלו האנשים בנשים"
So that the men shouldn't be able to look at them.
Now in the Yad the Rambam writes that the reason for mechitza is that men and women shouldn't intermingle [שלא יתערבו]. Some view this as a contradiction. But instead of making the Rambam contradict himself we can harmonize the two statements and say that both are true - we don't want looking and intermingling. Or that looking is a type of intermingling.
I heard one rabbi say that we as modern Orthodox Jews WANT the men and women to be able to see each other. We are not like those Charedim where the men are totally unaware of the women when they daven. We want the men to experience the special spiritual energy of the women.
והיה מחניך קדוש.
