My advice to you is if available, head out to an Apple Retail Store and see/use one for yourself. Apple Stores are all over the US and parts of Europe. Theny ou will truely get the feel for the computer.
I guess since you're switching over, some of the disadvantages would be that your windows apps will not run in OS X. Now that being said, since all new Macs have Intel processors in them, they can run Windows! There is a piece of software called Parallels that will enable you to run Windows side by side with OS X. It creates a virtual environment to run Windows in, but it DOES NOT emulate it! So it runs at 100% full speed just as if you had a PC sitting on your desk. Why is this important? Well this will enable you to run your Windows apps and get the Mac versions little by little. Depending on what software you have and how expensive it is, platform changes can be expensive. Parallels makes it easier to do since you can run Windows inside of OS X.
Some of the pros would be that you would be using a very advanced OS in Mac OS X. Its updated frequently, not every 5 years like Windows. In fact its in its 5 major release and its 6th will come out next spring. OS X works with multiple platforms which is also nice when you need to connect things like network drives and/or printers, etc. Its a fairly easy OS to use as well. The more you use it the more you know how to do things. And as always, you can come here to ask questions and someone should be able to help you. Just be sure to give as much information as possible. The more we have the easier it is to solve and issue or question.
If you don't want to use Parallels, you can use Apple's solution called BootCamp. The only downside to BootCamp is that every time you want to use a particular OS you need to reboot into that OS. This is free and comes preinstalled with Mac OS X, but you will need to supply your own copy of Windows. The same is true for Parallels.
Make sure there's printer drivers and scanner drivers for OS X as well. Nothing like buying a new computer and then not being able to use your peripherals.
Make sure you really want a smaller screen. The MacBook is a 13.3" widescreen and can seem small if you're used to larger screen. Also you'll probably want to add more RAM too if it feels slow, its because it doesn't have enough RAM. Since Apple just switched from PPC processors to Intel CPU's every OS X application needs to be ported over and not every app is ported over yet. So in the mean time, Apple has developed a technology called Rosetta that will allow a PPC OS X application to run on a Mac with an Intel version of Mac OS X. Rosetta uses a lot of RAM so the more RAM you have, the better.
