Is the Hong Kong 3 day MRT pass with a round trip airport express pass worth the $350KG?

Yes, the HK 3 days MTR pass that is worth the HKD 350, including two single trips by airport express and limitless MTR in 3 days.

I didn't see this before I went to Hong Kong and it turned out to be to my advantage. I bought a round trip Airport Express pass for $185 HKG and then used an octopus card to pay for all of my subway (MTR) and bus travel (note the 3 day pass doesn't cover travel on the buses). I went all over for 4 days and only spent $147 HKG for a total of $332 HKG, including the $9 HKG fee for the Octopus card (they hold $50 HGK and charge you $9 when you turn the card back in to get your $50 deposit back). So it depends on where and how you get there, but if you are going to use the buses that will cost you in addition to the 3 day MTR pass and probably isn't going to be the best option for you.