Michael,
Eruvim is fairly familiar to anyone who grew up, as I did, in a neighborhood heavily populated by observant ultra-Orthodox - and some Orthodox - Jews. As to whether it is a legalism or meaningful praxis, the answer ultimately depends on who you are.
To those who maintain the Shabbat in accord with their ancient proscriptions, the underlying rationale for its existence would compare with the older Christian requirements for observance of the Lord's Day as one on which work,
etc was prohibited - albeit on a much more stringent level than even that of the Puritans. The concept of Eruvim itself amounts to an
oekonomia introduced to make it feasible to function while maintaining what, in the civil world, would be termed a legal fiction.
To my mind, and that of many, it would appear to be extreme, but who are we to judge the religious praxis which others deem essential to their own observance.
A website from a local community here in MA which describes the praxis very well.
General Laws of Eruv [etzchaimsharon.org] Note that, in this particular town, which has a heavily Jewish population, the Eruv serves both Conservative and Reform congregations, as well as Orthodox. The accompanying maps and photos of "tricky spots" make the point particularly well as to the detail involved in this.
Many years,
Neil
