I had a good, reasonable manager, too.
I even think his reason for not letting me work out my notice was reasonable (huge liability for someone who's already checked out).
Do you think he knows that I immediately filled out my unemployment claim? Do you think he cares? I wonder if he thinks it's ok or it's somehow dishonest or something.
Anyways, even if you have a good boss and a job you like, don't give notice unless you are very concerned about the potential for going back there.
I wish I would have just sent a text two weeks from now saying “I'm not coming to work there anymore. Thanks for being a nice manager.”