I have been very happy with all my customer service from Exetel (two mobile services and ADSL2), but I am sad to say that my next phone purchase (my current one is 900MHz only) will probably be taking a SIM from Aldi. I understand that Optus' network is entirely out of Exetel's control, but the fact is that in peak times (i.e. 10am-2pm) I'm lucky to be able to even send texts at Monash Clayton, let alone use the internet or make a reliable phone call. My parents live up in regional Victoria, not exactly isolated at only ten kilometres from the Hume Freeway, but I have no reception at all when visiting (Telstra's network works fine, of course). Now that Telstra is starting to open up a decent proportion of their coverage to MVNOs, I'm really hoping that Exetel will jump on board and offer their existing stellar service with a quality network to match.
Otherwise I expect you will start bleeding customers to the competing budget operators we are starting to see cropping up.Cheers
Jarrad