Agreed, I am also a bit disappointed. What I have done is turn on vibrate + sound for my work email, and just sound alone for my personal email. That way when the phone is in the holster on my hip, I can at least tell whether the email is business or otherwise. Coming from a Blackberry, I never had any difficulty differentiating incoming email without looking at the phone.
Along the same lines, the mail notification in the top bar is the same for all email accounts. It would be nice if the little email icons were different colors based on which email account received email.