all carriers apart from telstra use the optus network, same with home phones. But some carriers on the home phones can use telstra lines it will cost you more a month though. So I dont think it matters what you use unless you go with telstra.
as for apps I did have a brewzor but didnt use it much and have not put it back on my phone since I reset it.
have a look HERE! thats a few but just searching homebrew but sure there is loads more
There are 3
Telstra
optus
Vodafone
http://maps.spench.net/rf/#pos=-28.9788097...l=17&tiles=[{%22t%22%3A%22u%2Fblack%22}%2C{%22t%22%3A%22s%2Fall%22}]