I got a Macbook after more than 10 years of PC-ing. It's more than easy, now I accidentally try to press command button on PC.
I just got it out of box, turned it on and just entered who I am and where I am, and thats it. It was ready. 5 minutes later I was playing with Photobooth. It connects to wifi seamlessly.
Security wise... All you have to do it turn on firewall, its off by default (its in System Preferences>Security). I read up on antivirus and Mac, and I decided I don't need one for my Mac. But you might want one, maybe go for Avast, if you access lots of public networks or get a lot file sharing with flash drives, etc.).
There is a cool app called Preview, that opens pretty much every image file and pdf, there is also a built-in unarchiver and so on.
I installed iWork, Keynote (the Power Point equivalent) is cool, Numbers also is better than Excel, but I don't really like Pages the text editor. I think Word 07 is best text editor. It's more intuitive and flexible than Pages, when I wanted to work with some tables, it felt like working with Word 97.
I also hate Safari, it's just as bad and slow as Internet Explorer. I got Opera and Chrome (Flash tends to crash Opera on Mac and Youtube doesn't work play anything on Opera).
Quick Time and that cinema app play most videos, but I had to install Divx and Flip4mac (wma/wmv support).
And I'm not sure about the Magic Mouse, it's not really that ergonomic, altho it feels cool (literary) and it has multitouch features and so on (I got BetterTouchTool app to manage the mouse better). It also eats batteries very fast, like in 10 weeks. So a different mouse if probably better.
Dashboard is cool thing, Stickies are better than in Windows and I really like how the apps and everything works on Mac, it's sort of "cleaner" than Windows or Linux.
I don't regret going Mac, there are things that I love, things that I hate, but all in all, they are good. I like how the case is seamless and it doesn't creak and squeak like other laptops (with exception of Sony and Dell) and typing is easy, keyboard is high quality, trackpad is great.
Go over the new to Mac video on Apple home page, it's really enlightening. And see a Mac in a store, play with it a bit and I think you might fall for it.
So, yes, I'd say it's a good choice, fast web browsing, music, some movies, little bit of photo/video editing, loads of text processing, ebooks, chatting (Skype, for mac it's somehow nicer than Win version, but it took a while to realize that), thats all I do and it never had a problem with problem with performance. 
