I did a search ("backberry macintosh") using Yahoo! instead of Google. The first hit:
http://www.blackberryforums.com/mac-users-corner/186-macintosh-blackberry-sync-requirements.html
There were more hits that looked helpful, but this one was quite interesting - you can do the search yourself - perhaps you will find something even more applicable to your particular environment. I do not believe it was suggested that there is a Google application that does Blackberry synching with Macintosh - rather, your using the Google search engine would provide you with information related to applications that can do that.
I use a Blackberry as well. My company IT wirelessly updates my Outlook email, Calendar and Contacts information (and when I make changes to either of those on my Blackberry, the same items on the Outlook server get updated, too). When I take notes on my Blackerry, I usually copy the notes, then paste them into an email and send them to myself. Tasks are Calendar items. The only reason I have to connect my Blackberry to my computer is to back up the Blackberry information - which, for all intents, is already the same as my Outlook stuff, so there really is nothing to back up and nothing to sync. If your company does not do this, then perhaps PocketMac from http://www.pocketmac.net/ may be of use to you. My company makes me use a HP/Compaq 6220 laptop and I need to VPN to our network to use the Outlook client, but I am much more productive when I use my Macintosh and OSX and Safari web browser - and connect to the corporate network using secure web browser access. The IT folks say this is not supported - which only means I can't ask them questions - but it was easy enough to get the security certificate and install it in the correct directory. I have help dozens of others do the same with their personal Macs. And they have helped others... and we're a company with 35,000 employees globally.
Then I did a Yahoo! search using "quickbooks macintosh" and the fourth hit looked most appropriate:
http://quickbooks.intuit.com/commerce/catalog/home.jhtml?_requestid=17359
In the upper right, Intuit says, "Want to manage your business accounting on a Mac? QuickBooks: Pro for Mac lets you manage your business finances on the OS you prefer." So that looks to be supported by Intuit.
Then I did a Yahoo! search using "excel macintosh" and the second hit looked most appropriate: http://www.microsoft.com/mac/products/excel2004/excel2004.aspx?pid=excel2004
According to Microsoft, an update is around the corner...
http://www.macoffice2008.com/
I use NeoOffice on my Mac and other than some pretty complex macros, I have not had issues with sharing Excel, Word or PowerPoint files with my Mac (and NeoOffice).
In either case, you could always not use the MacOS versions and run Windows on the Macintosh hardware (using Parallels or whatever) - in which case it is just like any other "traditional" Windows machine... that happens to have an Apple logo on it. But if you do this, be aware that you will need all the anti-virus, anti-spyware, anti-malware detection and eradication systems (and regular updates) a "traditional" Windows machine needs to remain protected in a networked (or shared media) environment that are currently not required under the MacOSX environment.
And, of course, you stated your option of returning to "traditional" Windows hardware (Dell, HP, etc...) environment. Technology is all about choices - and having the technology do what you need/want it to do. Having been an IT manager with responsibility for ~500 Windows and ~500 Macintosh computers, I can honestly say that I am forced to use Windows but I choose to spend my own money (and be much more productive) on Macs. But this could be different for you.