If you have ms office work, or graphics/design/video/3d work, faith plays a massive role in an Apple purchase.
As a pro or semi-pro doing any sort of work requiring real power, Apple is asking a lot of faith. So far, Apple has used up most of it while their powerful tower line is languishing without updates, and they are quickly making enemies with some of the biggest pro-app developers out there - Adobe and Microsoft. One can argue that technologies such as Flash and word processing spreadsheets are changing to be different standards or web apps, but things as powerful as photoshop will not move to a google web app any time soon, and others, like Final Cut/video editors, are not going to move to online versions until decades from now.
Apple's own pro apps (Final Cut Studio) don't take advantage of the superior aspects of Snow Leopard like Grand Central (and I think only Logic is 64-bit), and developers who have programs that are cross platform have very little incentive to take advantage of features that are Mac specific.
I just read an article in 3d world where some developers at Autodesk and Maxon said that Grand Central is awesome, but when you're cross platform, you're pretty much not going to use it because you need to solve those problems in a more platform agnostic way. Some of the other truly creative pro tools, like zBrush, are a constantly evolving product full of innovation. The mac version, unfortunately, often lags behind the PC version for years. That's not Apple's fault, but it's something a pro needs to consider when choosing to invest in a new computer: can it run the latest software? In a world where a new version can literally save you hours or days on projects, or revolutionize the way you work, you need access to the latest and greatest. If that ain't available on the mac, that's something to be seriously concerned about. Often plugins for Maya or C4d are available on the PC first, or not at all on the mac.
So far, there have been a lot of promises of what Mac hardware and software CAN become, instead of wowing us with what is currently available. That's enough to give anyone who needs the best tool for their money pause before making a significant purchase. Most of us have upgraded to snow leopard, but really, what's different about it in day to day use? It has it's good and bad just like previous versions of the OS, and quite a few show stopping bugs.
SL purged PPC code, but that only serves to alienate people with those expensive G5 towers- and tell them what the mac isn't, rather than what it will become.
As far as I'm concerned, I need some serious computing power. I'm going to have to weigh what tools fit in my toolbox. Apple has one more chance to come out with something resembling a prosumer line of their towers that I can afford. If they don't have it, then I have to consider that I don't fit into Apple's business strategy and move.
They will move forward with their consumer products, which really, are good enough for most people despite coming at quite a premium. Meanwhile, people who need to do more than the basics will be forced to look elsewhere and acknowledge that Apple sees more money to be made without taking care of the professional market.
