Though I am not a Mac convert, I have been using both platforms for the past twelve years–usually PCs as work and Macs at home. My Mac also runs Win 98 via the Virtual PC emulator, so I see the differences directly.
I think you will find far greater similarities among both machines–they both utilize the desktop metaphor and files and folders and run a lot of the same software (except for nich technical work, like your field). Windows seems to have slightly better “windowing” in that you can resize a window from any size. Mac can only be resized from the bottom right. But this is pretty minor.
I also tend to like the on-screen behavior of mouse actions(clicking and dragging etc.) on Macs a bit better.
Macs seem to be more intuitive, but Windows Explorer and Desktop are more functional then your uncustomized Mac Finder. That said, you can trick out your Mac with free and cheap shareware utilities that replicates and improves upon the Windows functions, so overall it can be another wash.
If your Mac is running the newer OS X, then it will provide the same multitasking pleasures of Windows. Mac OS 9 has mediocre multitasking as best, but it is faster than OS X for general navigation, though less visually attractive. The Windows transformation from say '98 to XP is a similar kind of visual improvement.
Windows applications seem to boot and perform faster, but the user experience just isn’t as engaging. Whether this matters depends on the context.
I still find Mac applications more consistent with eachother interface-wise as well. Windows toolbars can be less intuitive and amateurish as well.
USB and Firewire peripherals tend to work out-of-the box with Macs, whereas Windows machines involves hunting for drivers. Yuck.
All that being said, you will master the Mac experience fairly shortly.
Regarding the single button mouse–Macs work great with USB multibutton mice–I am writing this with the help of the MS 5-button programmable mouse. If you cannot upgrade your basic one-button Mac mouse, do realize that the “right-click” Windows functions are known in the Mac world as “contextual menus” and are accessible by holding down the control key. You can also get free or cheap utilities that allow you to activate the right-click functions by holding down the single button for a little longer bit of time and then navigating as usual. It actually works pretty good, but I have become addicted to the right-click as well.
For more information I suggest you try Google Mac-centric search.
Good luck, it’s the work and not the tool that really matters.