I don't find Macs to be too much different than a Windows PC. Most of the folder arrangements are pretty similar. I think the biggest difference is the lack of a "start" button. The commonly used applications (web browser, Word, Excel, etc) are displayed on the dock. You also have access to your documents folder from the doc. The doc is customizable too, so you add/remove items from it. Everything else (folders, other programs, etc) can be found by opening the "finder" application, which is located about where the "start" button is (although, come to think of it, I may have put the finder icon there…don't remember if it was there originally.).
Overall, I think I prefer OSX over Windows. The GUI certainly looks better on OSX.
iPhoto is terrible for organizing photos. Don't use it, except for editing. You're better off just putting your photos in the "pictures" folder, which is found in "finder". You can then organize it like you would on a Windows PC.
I find OSX is a bit more picky when it comes to renaming files. It seems like it only lets you rename a file if you open it in "finder".
iMovie is actually a pretty good video editing software. It is much better than Windows Movie Maker, and is much easier to use than Adobe Premier Elements. iMovie is my preferred editing software for the simple stuff that I do.
My parents have MS Office on their iMac. It works pretty well and no real complaints from me. Every now and then it freezes up though…lol.
The Magic Mouse is awesome too! It likes batteries though.
Back at my old job, we used Mac Minis for our digital signage stuff. They worked well for that. New ones don't have an optical drive, but that's the case with all of Apple's new products.