The high-level API currently renames unlinked files to ".fuse_hiddenXXX" and manages them using the standard file access callbacks provided by the FUSE-based file system. This creates poor performance for network-based FUSE file systems that already open file descriptors against files managed in a local cache. It's unnecessary to ever write such files up to a server.
For such file systems (including our recent work on FuseDAV), it would be better to just invoke unlink(), even while the file is still open.