After struggling with VirtualBox for a while, I broke down and bought VMWare.
I've never had any real problems with running VBox under OSX. I used to run VMware workstation on a windows laptop, but I always felt that the VMware OSX offerings were a lot less featured than the windows products. That, the VMware workstation licensing costs and the fact that the VBox application is basically the same on Windows and OSX drove me to VBox.
If I had the money lying around I would use VMware, but VBox does the minimum of what I need it to do.