Having lived in Leederville, I would say that it is great for couples and people who want to be near the city and it is also great for teenagers because the public transport is easily accessible and you have a choice between trains and buses. It is also close to the CBD. Leederville is a very expensive place in which to live. Although I enjoyed my time in Leederville when we lived there, I always thought that there weren't enough trees and parks and the traffic was always quite heavy compared to where I live now. That being said, I hang out in Leederville all the time and love the cafe strip and all the cheap restaurants and eating places that are available there. New ones are springing up all the time. The IGA supermarket is now open 24 hrs and there is a petrol station right next door. There are a lot of heritage listed houses in Leederville because it is one of Perth's older suburbs, so changes to some houses may be difficult to get through Council or take quite a lot of modifications and time to pass. It is an expensive suburb in which to buy and there is a mix of housing. If you are fortunate, there are still houses that have large gardens, but a lot of the housing in Leederville has become very trendy and there are unit type dwellings. If you want a home for raising a family, I would tend to look elsewhere. You can still get to Leederville really easily in about 15 minutes. I now live 17 kms from the CBD and that is how long it takes me in traffic if it is not peak hour. It is also cheaper to live further north.
There could be some benefits to living in Leederville in a house with back yard. However, there are many other places I would look at first - Leederville is getting more 'trendy' with all the apartments and the commercial and cafe areas. Less family, more singels and professionals for the future I would say.