Groucho, I share your enthusiasm for Iruvar. Brilliant movies failing at the BO are not rare; Karnan and Hey Ram come to mind immediately.
Iruvar was an excellent attempt at film making, but lacked in cohesion and of course in attracting the masses. It will remain as a moving testimony of Tamil cinema. Kudos to Maniratnam for even attempting the movie.
p/s: I remember reading that the movie's making was under tight secrecy and very little hype was created for it.