Apple doesn't "remove a user visible file system", they just make direct file system manipulation not as much of a necessity. And yet, this is not why their OS is good: it's because, if you want to, you can manipulate the file system and view it in as much detail as a BSD (OpenBSD) server, with just as much ease, combined with great hardware-software compatibility.
The system still has the complete filesystem implementation, and despite it not being visible to end users I imagine life would be much harder for developers without it, at least without replacing it with something likely to actually be even more complex (in code, not in UI). I mean, it isn't like VM or DTrace is "user-visible"; if anything, it is less user-visible/intrusive than its predecessors.
