has anyone experienced problems with this update.

jmarbis wrote:

After insaling

What does "insaling" mean?

I cannot log on to my mac?

What does this mean? That your mac won't start up? Or it starts up, but you can't log in to your User account?

Quite a few people have problems with every update. Almost always it is tied to third-party software incompatibility.

If you run into a problem like that, boot into Safe Mode. If that succeeds, it is definitely a third-party software issue.

http://support.apple.com/kb/HT1455

Some company's just can't be bothered making their software compatible with each release.

Yes. Updated 1 of 5 computers linking to files stored on a mac mini.

After completion the updated computer refuses to be recognised. Log in and Password refuse to be accepted by the host mac mini and all files are seen are 'read only. Alternative log in and passwords also failed.

Decision. Not update any other computers. Await Apple to sort the issues out and create an update for this mess.

... also noted that fails to log in using icloud .... 😟