The complexities of the Eruv are great, and the opinions as to its details many. Is it, in fact, worth it? Let's take a look, from the most pro to the most anti-Eruv views.
First, the Talmud, as we have seen, greatly praised the innovation of the Eruv as bringing unity to the people. Beyond that, without the Eruv, women with small children are virtual prisoners in their homes. Carrying a baby, or wheeling a carriage, would be out of the question. Rabbi Y.M. Epstein, the author of the Aruch HaShulchan, went so far as to say that wherever there is no Eruv, if a Jew desecrates Shabbat by carrying outside his home, the sins are upon the community rabbis (!), as they could have easily prevented it by a simple procedure. The presence of an Eruv in a community is often a major incentive for Orthodox Jews to move there, thus helping outlying communities to grow. Rabbi C.E. Shapiro, the rabbi of Munkatch in the early twentieth century, would always carry some object with him on Shabbat, lest he would be seen as one who scoffs at a fundamental aspect of Jewish law and tradition. (Remember, Eruv constitutes an entire tractate of the Talmud).
A middle ground approach is to allow, or even to encourage, the making of Eruvin in small towns, or sections of big cities that have no major thoroughfare transversing the city, which could constitute a Biblical Public Domain. This would accord with the view of Rashi, that a Public Domain requires 600,000 people. Some Ashkenazi Jews, and most Sepharadim, do not accept that view. However, since there are other considerations that can make a thoroughfare into a Karmelit, such as the view of Chazon Ish I mentioned in my last post. many of these will allow an Eruv "where necessary", but not for frivolous reasons.
There are some rabbis who are opposed to an Eruv other than for a small area, such as a courtyard. They consider the doubts as to what constitutes a Public Domain, and what constitutes an enclosure (is a wire enough?) too great to surmount.
Another consideration, sadly, is that the presence of an Eruv can, and has, caused anti-semitism. As I mentioned above, an Eruv tends to bring more Orthodox Jews to a community. There are those who do not wish that to happen. There have been a number of court cases in which the argument of anti-semites against the Eruv was ostensibly that if the wire crosses public property, it is a violation of the separation of Church and State. It is often possible, however, to make an Eruv which is totally unobtrusive. In my last community in which I served, I set up an Eruv that no one could know was there unless told.
Another aspect of the question was communicated privately by the Lubavitcher Rebbe to one of his followers, who was the rabbi of a large mid-western city. (Told to me by the follower). It is known that the Lubavitcher Rebbe was opposed to the making of city-wide Eruvin. The follower asked him why. He answered "the problem today is not that people desecrate Shabbat. but that they are unaware of Shabbat altogether. Every aspect of Shabbat that we make easier, makes less awareness of the specialness of the day".
In the early '80s, I lived briefly in Monsey, New York.. The Eruv was put up by a particular rabbi, whom some people did not approve of. As a result, part of the community used the Eruv and part did not. This caused needless division in the community. I chose not to use it, so as not to offend my neighbors. One Friday night, on the way home from synagogue with my then one and a half year old son, he sat down in a snow bank and refused to budge. No amount of coaxing would change his mind. A crowd gathered to watch. After about ten minutes, a man came up to me and whispered "in cases like this, we rely on the Eruv".(Today, Monsey has an eruv, that virtually all rely on). The Eruv was meant to bring unity. How sad that in that community it brought division.
I'll end this series with a story. A rabbi gave a weekly Talmud class. One young man came diligently, no matter how hot or cold. The rabbi eventually turned to him and said "you are my best student! May I ask why I never see you at services?" The young man responded: "Because I'm not Jewish! I love studying, and incorporate much into my daily life, but I am not, nor do I wish, to be Jewish!". The rabbis was puzzled. "Do you observe Shabbat? It is written that it is "a sign between me and the Children of Israel!". The young man said "Rabbi, I'm way ahead of you. i always carry a key in my pocket so as not to fully observe the Shabbat." "A key?" said the rabbi. "We have an Eruv here, it's allowed to carry a key on Shabbat!" The young man looked shocked. "What?!?! YOU rely on the Eruv?!?!"
May G-d enlighten us in His Torah, and give us Peace!