I moved from Aylmer back to Ottawa last year.
Comparing to Ottawa, houses in Aylmer:
-bigger lot
-lower price (50k+ on townhouse, more on single)
-higher property tax rate (but water is included)
-higher income tax rate (biggest factor playing here, I believe)
-better benefit (7$/day daycare, better health insurance, higher EI...)
-closer to downtown, 5 min to bridge, 10-15 min to downtown (but pretty bad during rush hour because everyone on the same road)
-cheaper grocery (superC...)
If you keep track of housing price, Quebec housing price keeps increasing even in 2008. Currently the difference between ottawa and Gatineau is not as big as before in terms of housing price. I wouldn't recommand high income family or young professionals to settle down in Aylmer.