With the standard mail application i can view html emails simply by opening the attachment.html attached to the email. With Nokia Messaging i can't view html emails.
With the standard mail application i can access the accounts of most of the email providers as long as IMAP4/POP3/SMTP is supported, thus 99% are usable (except crappy Windows Live Hotmail cause Microsoft is too lazy to provide that to its customers using FreeMail accounts - you have to pay microsoft to get this).
Looking is somehow annoying, no fullscreen mode.
And why should we pay for a service which is normally free for all? GMail, Yahoo Mail, GMX, AOL and many more. With Google Apps you can have free mail accounts using your own domain (eg. m@brett.com - hi mbrett :).
There is no need for Nokia Messaging.