I live literally 2 minutes from Longueuil. It is a very weird city. On the one hand, it is quite well located (compared to the West Island or Laval), most of it is grid pattern with sidewalks, and it has decent bus service for a suburb (The Terminus Longueuil is probably the Montreal area's best bus terminal from a passenger perspective). It has some of the basic ingredients that are required to build a real city.
However, there is very little private (or public) investment and development. Most of what is there was built between the 1950s and 70s. When these buildings were built, Longueuil had a very lax building code, and was a bit of a libertarian paradise. Poor people from Montreal (fleeing overcrowded conditions) and the country moved in (seeking jobs), and built homes with whatever materials they could find and afford. Today, it is built up, for the most part. However there has been virtually no redevelopment. In Longueuil, things do not have a tendency to get torn down and replaced, although low-budget renovations are somewhat common. Longueuil's population has been more or less stagnant since the 1980s (
http://www.stat.gouv.qc.ca/donstat/societe/demographie/dons_regnl/regional/Tableau_top_10.htm)
New development moved more toward Brossard, Boucherville and beyond in the 1980s. However, there is much more development in Laval and the North Shore.
Laval is kind of the opposite of Longueuil, also in a bad way. Its bones are much more suburban than Longueuil's, and most development has come since the 1970s. Despite being better liked by the provincial government with its brand new bridge, 3 Metro stations and five commuter rail stations (Longueuil has 1 of each), its busses have only about 2/3 the passengers of Longueuil's despite both transit agencies serving the same number of people (400,000). It has an extreme lack of urban planning, and is very disjointed and spread out.
I think I will have to do a Longueuil-centered photo thread at some point.