Tried this at Frankie's today. It's incredibly hard to describe.
The texture is like an *extremely* overripe mango. The flavor and aroma are both very similar to durian, but significantly milder. Durian is too intense for me but I've enjoyed things like durian-flavored macarons; it was like that. The difference between durian and this fruit is like the difference between biting into a lemon and drinking lemonade, or the difference between biting a garlic clove and eating something flavored with garlic. This is not to say cempedak tastes like lemons or garlic, rather just an analogy regarding intensity.
In addition to the durian flavor, there is almost a nuttiness. At times I tasted something that reminded me of Thai basil. And there is also a sort of acidity reminiscent of a slightly underripe grocery store mango. All these background complexities are hard to describe. But overall if you say 'extremely overripe mango texture, with the milder durian aroma and flavor you'd get in a durian flavored dessert, quite sweet, moderately acidic (*just* acidic enough to balance out the sweetness)' you are about 80% of the way there in terms of explaining it.
It wasn't my favorite fruit ever, but it was without a doubt the most fascinating fruit I've ever tried, because of how challenging it is to describe.
