I wanted to clarify:
There are poskim who permit see through mechitzos. The most prominent is Rav Moshe Feinstein ztz"l [see אג"מ ח"א סי' ל"ט - מ"ג]. My point was that not everybody agrees to this. See this teshuva that is כולו against Rav Moshe's psak. So I am not frummer than Rav Moshe. Not even close. But he himself says that ideally the women should not be visible to the men [today they have mechitzos that the women can see but the men can't which is a great solution]. In addition - the Rambam writes clearly that the need for a mechitza is שלא יסתכל. So the simple requirement of mechitza is that the men can't see the women. If the mechitza is not kosher- one may not daven there.
Here is the paradox: Rav Moshe says that one may have a mechitza that only reaches the women's shoulders provided that all of the women are dressed properly. So it emerges that in the more "modern" shuls [hey - I'm modern. I use electricity which is a modern invention] where the mechitza is usually low and/or see through it is a bigger problem because it is much more likely that some of the women will come dressed שלא בצניעות.
And in the really "farfrumpt" places [where fanatics like me daven:-)] where the women aren't visible at all - since the women who attend these shuls are usually dressed בצניעות - Rav Moshe's heter of a low or see through mechitza would apply.
So it emerges that Rav Moshe's heter either doesn't apply [i.e. when the women aren't dressed בצניעות] or is not used [in the more "Ultra Orthodox" (what a horrible term) places]. And liked I noted - ideally all poskim agree that the greater the separation the better.
קדושים תהיו - כל מקום אשר אתה מוצא גדר ערוה אתה מוצא קדושה
PS - I once heard a rabbi saying that we WANT that during davening men should be aware of the women and vice versa.
No - we really don't.
Anyway - he was later removed from his position because of breaches in tzniyus in his behavior. I wasn't surprised...
PPS - Ya think Donald will be maskim to have mechitzos at public events as per the psak of Rav Moshe?? They should tell him that part of the kashrus of the kitchen is determined by the sitting positions of the guests. And then of course Rebbetzin Melania will have to wear long skirts...