Brand is not just about spin - it's how customers relate to a company. Logos and advertising form a major part of that. We might not like it but how an aircraft looks isn't as important as other elements. As I said, how the aircraft looks is one of the smallest ways a passenger will see the logo. I'm actually serious when I say that a passenger will probably spend more time looking at the Qantas logo on their napkin that comes with their drink than observing their aircraft. We might not like that but it's true.
Will customers notice the change? Yes and no. Some will be explicitly aware of the change, others will simply realise that their monthly points email seems a bit different and fresher.
The challenge from a brand perspective for Qantas appears to be to capitalize on the elements you mentioned (history, safety, reliability) but also to be seen as up to date, modern, stylish, etc.
An airline can't just say that they want to focus on history and past reputation. If virgin position themselves as being hip and young and stylish and Qantas doesn't address that then there's a large market segment they loose.
Ansett disappeared fifteen years ago - so pretty much any flyer under thirty has grown up with Virgin - they don't see virgin as the new kid on the block, they see them as an established carrier. That's a major challenge for Qantas - they can play up their history and reputation but its going to be seen as less relevant over time by a lot of flyers. They need to simultaneously play homage to their heritage and look cool, responsive and not afraid of change.
So the new logo appears a bit hipper, the change reinforces to customers that Qantas is changing and is not afraid to improve (e.g. Combats concerns it's an old fashioned airline stuck in the past). The logo change isn't for pilots, it isn't for aviation enthusiasts - it's designed to look good on advertising and collateral (of which how it looks on the aircraft is probably the least important part).
As Qantas and Virgin battle for a twenty something frequent flier how the plane looks is the least important element. How the website looks, how the app works, will be more important than what the plane looks like nose into a gate.