The Longueuil metro area, while somewhat convenient, is not somewhere I would want to live. There isn't really too much in the way of services in the area (it is improving since the UdeS building has ground level retail). I think the closest grocery store is in Place Longueuil.
Longueuil's population has been more or less stagnant since 1991. It has only gained 5,000 people since then.
http://www.stat.gouv.qc.ca/donstat/societe/demographie/dons_regnl/regional/Tableau_top_10.htm
Apparently every census tract in Longueuil bordering the river lost population. It would be interesting to find out where these people went. Did they move further outward or move into areas like Griffintown (which apparently had a 123% increase since 2006)?
http://www.montrealgazette.com/opinion/Population+spikes+Griffintown+Laurent/6124253/story.html