Some people like it. Some don't. I'm finding that, of the people that don't like it, most are primarily corporate users who are used to the iPhone and Blackberry way of doing things. They want to see how many unread messages there are, but don't always have time to go through every one of them. The problem here is that they might open mail to answer one or two messages, but don't have time to address everything. When the mail app is closed, now it's out of sight, so there isn't the constant reminder that "Hey, you still have mail to look at!".
Again, for home/personal use, most mail can wait anyway, so it's not a big deal. For corporate mail, it's usually more of an issue. My suggestion is to at least let it be set as an option.
Also, I have multiple watched folders under my work inbox. I only receive notifications for the Inbox...not any of the watched sub-folders.