I still can't get enough of my musing over Google's anti spam movement . I have always been an advocate of Linux, opensource and other stuffs. I love Google, and still aspire to become one of their proud employee one day, even just to be seen by them would bring me to orgasm! 
By far, I cannot and would not compare their services to any of the other leading service providers. From email, to groups, to shopping, to chat, etc. Of course, what I love the most from Google is their uniqueness and very genuine, yet sometimes crazy ideas. What I tend to imagine about people inside Google is that they often chat about world peach (nah!), or anything that inspires them, then wham! A new born idea! Its great how they can twist one technology into another.
GMail has been around since 2003 and I have been around that long too to have witnessed the evolution of their client and its services. Soon after, many other products have caught my eye, and had never let me lose my fascination for it. One of the cool features I've learned from GMail, is that you can have your corporate mail sit inside GMail itself. Its like having your mail domain serviced by GMail. And what's good about it, is that you get to share the usual 2GB space for your mails, and everything else that GMail can offer.
Some do ask why bother getting a new email inside GMail, I think the concept of clustering your mail conversations is simply better than reading a long list of sent and replied mails from bottom to top! Sure, I love my Thunderbird client.. coz it keeps me technically invisible from the net (as in away from GMail's chatboard, offline from Yahoo! and/or Skype). It gives me time and space to focus on my reading of mails and/or nocturnal programming, but it just cannot be any better for rendering long email conversations. Standalone email clients can serve as offline storage of mails, I think, by far, that is one of GMail's drawbacks. If you use it for your corporate account, then, you cannot ensure that all conversations are logged offline in their PCs.
The ads inside GMail has never seemed disturbing to me, not even a bit, that is why I don't believe that using GMail is any worse than using other email service providers. I love it simplicity, that the ads themselves almost seem like blending inside your interface. Good for them (ad owners) and good for us (end users).
This service of theirs, though seemingly expensive, is actually free with some limitations. They do offer a premium, but you can easily see that even the smallest business network can get their own corporate email addresses through GMail, even without securing an expensive mail server for that matter. Even the standard setup would do just fine.
With all of this said, I still believe that if a huge company is to be considered, getting a dedicated server would be better. 