Out of the Unbound stories, this is one I am most neutral towards.  It is not bad.  It's pretty cool.  It's a fun alternate take on the Third Doctor era.  The performers definitely make up for a script I found otherwise pretty boring.  David Warner's Doctor definitely stands out and it is cool that he would return to the series later on.  I can definitely see why the producers chose to do so.  It's a very fun role for Nicholas Courtney too, and one that shows even late into his career, he really had this enormous range and brought so much life to what could have been a one-episode role.  David Tennant playing Col. Brimmicombe-Wood is very fun, being about as despicable as he would be when they return the character later in the original UNIT series.  I like that Big Finish kept a bit of continuity built around Wood by introducing the main universe version of the same character from this series, that's a neat little detail in the history of this franchise.  And Mark Gatiss playing the Master was fun, that really felt fitting for him as an actor.  Plus he would also get to return to the role in the future, another pretty amazing little detail.

So the casting has a lot of cool stuff going on and it is a cool production because of it.  The Hong Kong setting works okay but this is not a time when Big Finish even bothered to hire actual Asian actors so I question it, to a degree.  It feels very off because of that, and the plot around the Ke Le was pretty boring.  They really just felt like generic zombies to me.

Overall, it is a cool story with lots of interesting trivia relevant to the franchise.  Absolutely worth checking out for fans, but definitely not the best story in the world either.