At 150K that mdx doesn't owe anything to anyone. You can expect anything to go out at this point, and it will largely depend on how it was serviced during those 150Ks.
I would factor replacement tranny into price (call around, call Acura), and effectively 150K MDX price + 3-4K(guess) for tranny = price. If you can live with that, should it happen, you'll get new tranny (rebuid?) plus warranty on the new tranny and if it doesn't happen, bonus.
Price 100K MDX, compare and see what you are working with...
In conclusion, MDX is very good for what it is, also it is easy to follow up on Mercedes and BMW for reference (I just never see much of anything from those with 150K especially in SUV).