Again with the Google Apps vs. Microsoft Exchange!
Google put out another one of their "Google Apps vs. Microsoft Exchange" webinars. The quote from Google is, "Many companies are faced with a choice: upgrade to a more costly enterprise license for Microsoft Exchange or find a business grade alternative at a better price."
If you want to do an apples-to-apples comparison, then you must compare Google Apps for Business with the hosted version of Microsoft Exchange from a vendor such as Rackspace. Comparing Google Apps to an on premises installation of Exchange is disengenuous because it is not an apt comparison. Comparing Google Apps to hosted Exchange means that you are looking at cloud-based email services from different vendors.
For businesses & workers who utilize Microsoft Outlook, hosted Exchange services works well. I know that Google Apps supports Outlook, but it is just not the same. Or if you prefer to just use a web browser, Exchange's Outlook Web Application (OWA) + Internet Explorer offers a feature rich web-based email experience. Google Apps + Chrome looks the same as does Google Apps + Firefox or Google Apps + Internet Explorer. Plus let's not forget the integration advantages offered by Exchange if you run Windows Active Directory for identification & authentication.
As for mobile support, with the advent of Exchange Active Sync (EAS), practically any modern smartphone can hook directly into an Exchange environment. I myself use an Android-based smartphone with both Gmail & Exchange Active Sync running on it and there isn't much difference between the two clients.
Google touts the fact that they use Postini Services for effective spam filtering. If you go with hosted Exchange services, the vendor will also do spam filtering. Most anti-spam technologies these days are very good and rely upon the same black lists so I'm not sure if Postini Services is leaps & bounds ahead of what others can offer in terms of blocking junk emails.
I'm speaking about all of this from first hand experience. I have two entities that I'm responsible for. The first is an organization with 50 employees spread across four locations plus teleworkers. I run my own internal anti-spam & email servers. By doing so I'm able to access any & all message traffic to & from the three email domains that I operate. For the smaller of the two entities that I'm responsible for, because I started them out from scratch, I went with hosted Exchange services. Initial setup & configuration were straight-forward and so was the setup for each individual mailbox. Configuring Outlook to use hosted Exchange was also a simple process. But I get this feeling of dread every month when I get billed. I feel like I'm being nickle & dimed as I'm charged for each & every mailbox. You want a mailbox to use for public postings, that will cost you. You want a mailbox for a logical group of users, that will cost you too. With my on premises Exchange server, I can create, modify, and and disable mailboxes as needed. Google charges $50 per year per mailbox while Rackspace charges $156 per year per mailbox. Pricing should be a primary consideration when weighing your options. Remember that with both vendors, as you add mailboxes, you add costs so your OpEx goes up. Do you own calculation for my setup - more than 100 mailboxes spread across three (3) email domains. Whether it's Google or Rackspace, they'd charge me for each mailbox in each email domain so in fact I'd be looking at triple the cost. From Google I'm looking at $150 per mailbox each year and from Rackspace I'm looking at $468 per mailbox each year. Wow, that is a lot of money.
As I'd mentioned earlier, I run my own anti-spam & Exchange servers on premises but not inhouse. I've put these system into a collocation facility. One of the benefits of a collocation facility is that along with the messaging system, I've re-located other internal infrastructure critical systems into the facility. Some might call this setup a "Private Cloud." I refer to is as Business Continuity. I pay the same amount each month no matter how many mailboxes I create plus I have protection for my internal infrastructure and that is something that Google can't do.
My goal as the Technology Manager for a small organization is to offer cost effective messaging, identification, and authentication services to the business. Management must be able to control who has access to what and when they have access. Running Exchange internally allows me to do this.