I expected something bigger as well. From the release mail of Linus:

  It's a pretty normal release - roughly 60% drivers, 20% arch updates,
  and 20% "all over" - filesystems, documentation, tools, you name it.

  Nothing hugely special springs to mind - there's some memory
  compaction issue that is still being discussed, but I don't think
  there's anything particularly scary or special that stands out over
  everything else in the -rc1.

Well... The Systemtap userspace probes seem nice, as does the ext4 metadata checksumming, CODEL queue management and the connection repair (albeit I have only played with the idea of moving a live VM from one box to another).

Yes. They are significant. Not as significant as the delta between Solaris 10 and 11 or Windows 7 and 8, but, considering the time elapsed since the previous significant improvements, I'd think it's quite impressive.

Incremental improvement is good.

If you don't have graphics support for your current card or need the new profiling it's significant. The "target mode" is cool but it's not a significant use case.