I’m a big fan of the “Improves networking reliability” item, since the network stack had gone partially dead as it has been wont to do (even as a side-by-side computer on the same subnet proves that nothing is wrong with the LAN or internet).
The OS X Yosemite v10.10.4 Update is recommended for all OS X Yosemite users.
The OS X Yosemite v10.10.4 update improves the stability, compatibility, and security of your Mac. This update:
- Improves networking reliability
- Improves Migration Assistant reliability
- Addresses an issue that prevented some external displays from functioning properly
- Improves the reliability of upgrading iPhoto and Aperture libraries to Photos
- Improves reliability when syncing photos and videos to iCloud Photo Library
- Addresses an issue that could cause Photos to unexpectedly quit after importing some Lecia DNG files
- Resolves an issue that could delay outgoing email messages in Mail