I think it is a good idea. There are people who really really have a thing about sitting at a bulkhead or exit row and would be willing to pay for the privilege. A lot of pax really enjoy (?) these seats and like I said some do so much that they would happily pay charge. If you pay the charge (and fit the requirements - most frequent pax know if they do or not) then you are guaranteed that seat. You don't have to suck up to the gate staff!
Also if Virgin makes a little profit from it whilst making their customers happy then good on them. They are not an airline for charity!
Why aren't they doing it for say $15 or $20 on shorter routes? The demand would be there.
I also think they should perhaps offer the 'Blue Zone' pax a $5 voucher to use on the A La Cart so it doesn't seem so "tacky" as you put it. Makes it look like you are paying for a premium service... Just my opinion.
The reason QF won't do it is because it views itself as a "full service" airline. There are just some things that such carriers can't get away with. Another would be to charge for soft drinks, as an example.
The british charter airlines have been doing this since time began. Nobody seems to care over there. Australians are so afraid of change when it comes to air travel. When we stopped doing hot meals (on 40 min flights!) we went through hell and back! Seriously, the two months afterwards were just hell. FAs were getting abused and food thrown back at them - it wasn't fun at all!
Virgin is here to do things differently. Even QF has had to change some of its practices as a result of DJ. Air travel is heading in a different direction (all over the world - not just in OZ) and it will take time for travellers to get used to it....