In their rush to get the product out to the customers…

Apple have obviously made some significant backwards compatibility errors. Firstly, there’s the firewall – altering the on-disk content of applications to make them signed when you accept them. Its an interesting approach, but it’s complete pants. You don’t go around altering binaries on disk. You create a detached signature! It’s not really bloody difficult.
On Vista, you can see *every* rule that exists for the firewall. On Leopard, you only get to see the exceptions you created yourself.
I’ve been having random application crashes. They seem to be related to drag and drop operations that went wrong.
the calendar application does not want to talk to my instance of davical properly (all the calendars disappear after restarting, and I get an error every time I create a calendar).
Then there’s the ‘the application terminated unexpectedly’ – no, it didn’t, I used the <Apple>Q menu item to quit the application.
Context sensitivity on the mail application is kinda limited – It doesn’t detect URL links properly – I have a site that’s called http://foo4/…, and all the link comes up with is http://foo. As I said, a bit limited.
Overall, though, the experience is positive. I would have preferred if apple had simply spent some more time testing the damned thing against anything other than their own applications and services.
And, as soon as they allow a replacement for .mac that can be replaced with an external, non-proprietary service I’ll be a happier person