I use other sites (ExpertFlyer and ANA) to find routings and then verify availability on the Aeroplan site on the exact date before I call in. The most compelling reason to use another site is that it is a COMPLETE pain in the ... to search across multiple dates on Aeroplan's site. Regardless of the site, you are better to search for, say, IAH-IST across multiple dates and then find a connecting flight YVR-IAH on the date rather than just typing in YVR-IAH.

Mark