The following points have been observed on my Synology DS414, but I would think that most of them are due to the software stack, and not hardware specific.

• DDNS updates with FreeDNS require explicit use of username and password, instead of allowing use of the authentication token.
• DDNS update interval seems to be hardcoded and not configurable (through the DSM UI). I’d prefer the NAS remain hibernating at night.
• The AFP (Apple Filing Protocol) implementation is based on the old-ish version 2.2.3 of Netatalk. Netatalk requires a separate database to record file to id mappings (managed by cnid_dbd) which is purged by the NAS on every reboot. This database is created as soon as a user connects to the volume via AFP and can take multiple hours to build if the volume contains many files. This makes all other accesses quite slow while the database is rebuilt.
• Hibernation leaves fans running.
• If your AFP connections to the NAS reproducibly crash and disconnect (with very flaky behaviour on the Mac, no clean dismount, endless reconnect retries and replays “AFP_VFS afpfs_DoReconnect” when attempting to create a Spotlight index on the NAS volume, a likely cause is problematic extended attributes on files on the volume. These can be removed (after ssh’ing onto the NAS and going to the correct shared folder) with 

  find . -type d -name "@eaDir" -print0 | xargs -0 rm -rf