The truth is, Office is becoming less and less of a good product for the SMB market, especially on Windows. On the Mac, it's a better fit, but that's only partially due to product design. The truth is, a lot of what WinOffice does simply requires Windows. So MacOffice is still a decent choice for the SMB market, but it's a mix of targeting and accident. But even without the infrastructure overhead, Excel on the Mac is still Excel, Word is still Word. They're big semi-truck applications, with the kind of learning curve you have when you learn to drive a semi.
Enter iWork '08. It's not trying to beat anything. It's not even all that integrated, not compared to Microsoft Office. What it is however, is a collection of the stuff that people in the SMB market are most likely to need. A solid word processor that can round-trip most Word files. A spreadsheet application that covers the most common use, and can deal with a large percentage of Excel files. A presentation application that can make the worst tripe look at least decent, if not good. You can use every feature in iWork without ever needing a groupware server, a directory services implementation, a collaboration server, a videoconferencing server, etc., yadda.
Since a trial version of iWork ships on new Macs by default, you already have it. So that means, with no applications that are designed for experts, by experts, companies that don't want or aren't able to deal with all the back-end that Office really wants can still get work done, and have it look good. They can juggle numbers, and if needed, they can make some great presentations. Mail and iCal and Address Book aren't Outlook, but then again, you can get their full feature set for a lot less time, money, and aggravation than you can with Outlook.
I think Apple has looked at Microsoft Office, especially Office 2007, and instead of saying "Wow, we need to beat them," they're saying "Wow, they've really forgotten the SMB market, especially the "S" part, and that people want to be useful without thousand-page manuals, and classes, and directory/server infrastructures. Microsoft Office has, over time, gradually stopped being all that great a choice for the SMB market, especially on the Windows side, and become something that will do anything you want, but at a price.
iWork '08 is saying "You don't have to pay that price. You don't have to buy an H2 just to drive to the store to pick up a quart of milk. You don't have to become a civil engineer just to put together Ikea furniture. There is another choice, and we have it." Even allowing for converting from Windows to the Mac, when you add up all the costs of the infrastructure WinOffice really wants, especially with Office 2007, iMacs are not much of a penalty after all. Not making your IT setup really complicated will save you most of that money on its own.
So no, I don't think iWork '08 is any kind of shot at the Microsoft Office infrastructure and/or the enterprise. Rather, I think it's aimed at the people Office has left behind, and that is, when you look at the SMB market, a lot of people with a lot of money. That is who I think iWork '08 is aimed at, and if I'm right, Apple stands to do extremely well over the next few years.