wow…you can see some people with such an attitude here. I agree with Bluetortilla, if your response does not bring any contribution to the discussion then don't bother writing.
Well, it terms of the subject, it's true it has to be a bug, if you want to use full screen in Mail then you should also be able to navigate trough the other emails in your inbox, weather in a separate desktop like in mission control or having a smaller window for the email you are composing but having access to the other emails. Of course, some of you would say "they don't push you to use it in fullscreen" but to be honest I see that answer as they don't have the correct answer.
In my case, I love my mac, I love Lion, I love fullscreen apps, but I need to navigate back and forth when composing or replying. So I came up with this: You can be weather in fullscreen or standard, then you click new mail, or reply/forward an existing one and once the new window with the email comes up you can go fullscreen in the main window from Mail, or if you are already in fullscreen you have to go standard and go back to fullscreen. That way you'll be on a fullscreen Mail with a new email, reply or forward window in a different desktop. I know it sounds complicated and boring to do it every time you need it, but at least it works and you can use multiple screens with Mail in fullscreen, which at the end is what I was looking for.
Let's see if Mountain Lion fix this bug, even when some of you would still say it's not…
Best,
HH