When I use Touch ID to log in, after it recognises my fingerprint, it often takes 5-10 seconds to actually let me in. It doesn't happen all the time but most of the time. Any ideas what that could be?
That definitely is not normal behavior. Have you tried reinstalling the OS or creating a second user account to see if the behavior continues?
With a factory install of the new MBP, I had a several Safari 'quit unexpectedly episodes, along with an app or two not installing and or subsequently work as it should. I reinstalled the OS new without migrating and the MBP has been working as it should.
If you have tried the usual reset methods thus far with no results, make sure and file a bug report with Apple. You don't need to be a developer to do so.
Im going to do a fresh install first and see how that goes, I've experienced a few "glitches" and error messages since setting it up so I think a fresh install is a good idea. I do log on to an Active Directory domain but my user account is mobile on the Mac so that shouldn't delay authentication at all, it doesn't have any issues on my other Macs.