I've admittedly only done this with simple projects. But still, for those simple projects, "flawlessly" and "5 minutes" were not exaggerations. Even if a full-sized project ends up revealing some small gaps in the abstraction, it's still miles better than the alternative.
Ok, well, for the small projects I worked on, “flawless” was “not even close” and “5 minutes” was “surely you must be joking”.
I think this is more of an indictment of the Android NDK than anything else.
A bit of this is also just the fact that with Unity you don’t have to personally deal with the Android NDK, which is the software used as punishment in the fourth circle of hell, if I remember Inferno correctly.