eCryptfs has a lot of use right now. It's what (e.g.) Ubuntu uses to implement secure home directories. It's not a block filesystem, but it is a filesystem. (You mount it on a directory; it's just backed by a directory of encrypted files)
IIRC, there has been criticism of the implementation, and possibly the design. This may be what is referred to.
There are also things like EncFS, too. I'm not sure what the view of some of these other filesystems are from a cryptologist point-of-view.
Pedantic, but important: there's no such thing as a "block filesystem". There is encryption performed at the level of a filesystem, and encryption performed at the level of a hardware device (schemes like Truecrypt are, in fact, simulating hardware disk encryption).
It's a little ironic that encrypted filesystem implementations on Linux are so bad, because the filesystem is a much better layer at which to perform encryption than the device itself.
This is true. I was pointing out that eCryptfs is reading files off of another filesystem, and presenting the decrypted versions of the files as another filesystem vs. something else that can read directly from a block device.
