Marketing goes both ways since the FFA itself markets the game poorly IMO. Here in Melbourne you'll find it rare to get advertising for matches except against Sydney.
Quality of the games are what you would expect though, but the form swing is quite extreme. Unfortunately the league is losing its players to other leagues (sometimes to England lower leagues, some goes to China or Korea and for those who wants the money they go to the Middle East teams). A-League has a variety of players; the star foreigns like Carlos Hernandez and Robbie Fowler, the Socceroos like Jason Culina and Craig Moore, the youths like Kofi Danning (unfortunately out for the season), Tommy Oar, and Mate Dugandzic, and lots others. Mostly it's a hit and miss though. One week you find yourself watching a very awful team and the week after that they looked like they can beat anyone.
As for Brisbane you'll be watching a team in its rebuilding phase. Early this season they have been one of the basket cases and after they sacked Frank Farina, new coach Ange Postecoglou is starting to remove the supposed deadwoods and try to emphasise on youth in the team while salvaging a season to reach the finals. They're currently on a quite good run so you might get a good performance by the time you arrive here.
Because of the earlier mishaps (huge increase in ticket price, poor home form) the crowds went away and they might start to return. You might expect to find crowds in the high 9000 or low 10000 in a 50000 capacity stadium.
PS: Never bet on A-League matches
it defies logic to the extreme.