It all depends on what you want out of your IT infrastructure. I am a proponent of a server, in terms of user management, security, centralized storage and backups, and secure remote access. The uniformity that Active Directory allows a central location for user management, security, and profile storage; not to mention it means that Windows Networking works with few quirks.
The nice thing about keeping Exchange (email, for that matter) in-house is you have your finger on its pulse at all times, and the people who run the place have a face and a name when things go badly. And in my experience, I run over-all about 25 regular sites with Exchange 2003 and we have NEVER had a failure. And I refuse to "knock on wood" about that, too. It is all about the hardware. If you build a good machine with server-rated parts -- I prefer Intel motherboards and Western Digital RAID Edition hard drives on a good RAID controller (3-Ware has been my staple of choice, but I also like the Intel Matrix RAID controllers* and Promise RocketRAIDs as a bare minimum) -- you will have long-term good results.
It costs more up-front to do it this way, between the hardware and software, but the long-term benefits are outstanding. I can build a Small Business Server 2008 system for around $3000 for 10 users. Bearing in mind that a large part of that cost is the software. But, frankly, I have never been in a jam which I could not fix in a short amount of time or I could not get Microsoft to help with (especially if you are a Registered Partner and have the Action Pack, which gives you business-critical support for free!)
Okay, having said all that, there is certainly a benefit to going with an outsourced hosting like GMail for Business. In particular, there is not expendature on hardware or software, and no administrative over-head other than setting up email accounts and your Outlook clients or whatever other devices you want. Support, well, not so much as I have come to learn, but the support website and forums are not shabby.
The down-side is you are beholden not just to your Internet connection stability, but the links between you and Google. Not to mention the regular outages suffered by GMail, which happen at least once a week for varying areas, but it is only that wide-spread outages which make the news. And, of course, you are putting your data into someone else's hands, especially with Google which aggregates EVERYTHING it digests into variuos services and products, with the occassional security "whoops" which can expose the data for "less than 1% of users for a short period of time." (Paraphrased, of course.)
So, that is my take on it. Again, I like having everything in-house so I have control over it, and know what to do when it breaks other than wait for someone else to fix it. But, there again, MY uptime and reliability in-house is much better than that of Google. Or 1&1, for that matter (UGH!)
* Intel has its issues every so often, most recently was a bad Matrix driver and manager update which would drop drives from arrays. But a minimal issue in the end, since regular troubleshooting was able to figure that one out. As well, its products carry a three-year warranty, and you can get advanced replacements shipped Next-Day. Personally, I would love to push AMD kit, but AMD cannot touch that even in its wettest dreams.
Hope this helps.
