I notice from the oneworld website that The House lounge is near gate 51. For those who don't know SYD T1 well, this is the "other side" of the terminal, so it'll be a few minutes' more walk to get there from BA check-in and a few minutes' more walk to get back to the Qantas side of the terminal which is where (IME) BA16 usually departs from. Not a deal-breaker, obviously, but if one is thinking of small details then this may be worth bearing in mind.
If this is intended to be a relief lounge for the QF business class lounge, then I can see why it might be worthwhile given how busy that QF lounge can get at times.
In contrast, my experiences of the QF first class lounge are that you might have to wait for a proper dining table if you want one, but there are always plenty of other places to sit (including at the bar facing the kitchen) and you can eat off the whole menu wherever you are in the lounge.