I have been using free google account for many many years, it's a great product helping many small business running their daily tasks.

Recently I upgraded my google account to their business plan, and I think,

it's mandatory for small businesses to use Google Apps. as part of their daily routine.

Now, what's great about upgrading your free google account to their business plan,...

1. Syncrhonization.

With their business plan, you can synchronize your gmail, google calendars, tasks, and even contacts with your outlook.
Synchronizing with outlook is important, so that we still have access to our contacts / calendars when the internet is off, on the other hand we have my emails/contacts etc in google cloud as a backup.
For those android lovers, you can also sync. your contacts with your phone, this makes double backup.

2. Customize your email address to your domain name.

Customizing email address, we can send out emails under yourname@yourdomain.com instead of using youraccount@gmail.com.

Sending out emails using your business address is important to maintain integrity of your business, people tend to take you seriously by having this in place.

Back in the days, you can do this without any cost, apparently things have changed.
 

3. Access to more google apps. 

4. Offline access to google drive.
What's better than having auto backup ?

Losing data is frustrating, every small businesses know that they need to backup their emails, documents, contacts and many more.

Your harddive is not a very reliable medium as a backup storage, with google drive, we can sync data in our hd with the one in the cloud.

5. UNLIMITED space for only $10/month/user.

You can't get better than this, for only $10/month/user you get all access to Google apps and unlimited space for your email.