There are a lot of different definitions of what a flashpackers hostel is but I generally think of it as a brand new purpose-built place that is meticulously clean and maintained to the same standard as a brand new 3½ star to 5 star hotel, but with bunks.
However some hostels call themselves flashpackers because they have en suite facilities or private rooms. Really that doesn't make it a flashpackers if it is an old run down building.
Nomads market their Legend Has It… Westend hostel in Sydney as a flashpackers. It is an old building that is nothing like what I expect a flashpackers to be and by calling it a flashpackers they are bring down the reputation of their hostels that actually should be called a flashpackers, such as their excellent Nomads Industry in Melbourne and the Serpent Hostel & Bar in Cairns.
Some flashpackers hostels that I have recently visted in Australia are:
Beaches of Broome (Broome, WA)
Gilligan's (Cairns, QLD)
Sydney Central YHA (Sydney, NSW)
Wake Up! (Sydney, NSW)
Nomads Industry (Melbourne, VIC)
Melbourne Metro YHA (Melbourne, VIC)
Urban Central (Melbourne, VIC)
Grampians YHA Eco-Hostel (Halls Gap, VIC)
Some of these are really outstanding. For instance Beaches of Broome (not connected with the Beaches hostels on the East Coast) is just like a fancy resort, but with bunks. From the street it actually looks nicer than the four-star resort a couple of doors down the road. However it doesn't have the charm of more established places like the Kimberley Klub, also in Broome, which would have been classed as a flashpackers 12 years ago when it first opened but now has a more established feel as it has lost some of its gloss but gained a lot more atmosphere over the years.
Flashpackers' hostels aren't for everyone and most travellers prefer something a bit smaller with more atmosphere but there is definitely a place in the market for them, especially in gateway cities where travellers will spend the first couple of nights of their trip. In these cities something clean and well maintained with top quality facilities makes a nice soft landing before staying at older cheaper hostels.