I'm sorry to hear about your bad experience with VN, their 777's are definitely showing their age, the good news is, they are on their way out (2 have already left the fleet), although they have refurbished 2. VN will start receiving both A359's and 789's next year so that will definitely improve customer experience, CDG is slated to be the first A359 destination while LGW will be the first 789 destination.

VN is still a very good option for flying to Australia, their flights to MEL & SYD are quite good, it helps as the A330's they operate the flights with are quite new. I myself, have never had trouble flying with VN, besides the odd delay, though they still have a lot to catch up to with the likes of CX, MH, SQ, TG and more recently GA.