This is the case in 4.5 as well. I battled this yesterday.
Walter, in truth your problem is on the client side. Not all users get that warning--you can turn it off on the client. I think my solution was to put an interim page in that said "Thank you, you are now logged in", and issue the redirect from there. That's your solution, too, right?
Our experience has been that a lot of our users don't notice that they got logged in, and are confused when they are presented with the home page again (when they login from the home page anyway) and I think the extra "thanks you are logged in" page would make them feel better.
