I have 12 mail accounts with most of them being GMAIl so I cannot use MAIL for all of my Gmail needs as it just doesn't offer the full scope of Gmail
I use
MAILPLANE. Its not free but i paid little for it. $30
Im like most people, i HATE to pay for software and will use the free edition but on OSX I have only paid for 2 main ones I feel I need. One of them being MAILPLANE.
Its $30 and worth EVERY penny in the time I save using it.
It only handles GMAIL but it sets up your imap folders exactly as if you were in it on the web, so you have all the ability to see, delete ALL mail, Spam, and any other folder that isn't quite as clear on MAIL I find.
When I used MAIL, i had to go on to the web every once in a while and clean out folders but through MAILPLANE i get everything.
Its easy to switch into the settings as well, just as if you were in the web but without having to go into the web each time, which would be annoying to do
For someone that only uses GMAIL i find it much more sophisticated in all you can do with it than MAIL for gmail
http://mailplaneapp.com
And it notifies me of ALL my Gmail, all 12 accounts
This wills show you a comparison between MAIL and MAILPLANE for gmail accounts
http://mailplaneapp.com/comparison/
Now IF i didn't want to pay for a great program and had only one GMAIL account, Id use MAIL but I found that I had to go into the web every couple of days to find hidden emails that despite ones best interest aren't as easy to see through MAIL
With 12 accounts that is too much work.
MailPlane just lets me switch quickly from one account to the next so of anyone using several GMAIL accounts, I personally could not live with the challenges of MAIL for gmails