There is an easy way to have your entire number of new mails show up in the dock icon - use SmartFolders rather than rules. I replaced all my rules with equivalent SmartFolders. Now when new mail arrives I leave it in the InBox (which means the total number of new messages is listed in the dock icon) but I still have individual folders for viewing messages based on the criteria I choose.
In fact a message can appear in more than one folder - say if you had a folder that had contained messages from a mailing list and a separate folder for a friend who also happened to be on that list - messages no longer have to be either one place or another, via SmartFolders they can be found in either place.
The new Mail toolbar is something of a travesty - I don't think it's as hideous as some people, but it's obviously a step back from the sort of interface clarity Apple is known for. Hopefully they'll get the message and Mail 2.1 will switch the chrome to something better.
As for the drawer, I'm glad it's gone. The sidebar is much more consistent with other apps and as Maarten said, it's more accessible.