Im using my PB for 2 years now as my main machine, since my PC died. I got to say, if you're a new switcher you're going to be missing a few things. But dont worry, they could be replaced on the Mac.
Coverting Videos to iPOD:
If you used Videora on PC, use iSquint for Mac. People will recommend other ones, and I've tried them all, and they all miss one feature: 100% guaranteed demuxing. Only iSquint does it EVERY TIME. What demuxing does is it separates the video and audio in a MPEG file so that they can both be converted into MP4. If you use anything else, all you'll get is an MP4 video, with no sound. ffmpeg claims to demux well, and it does, just not 100% of the time. Download ffmpeg also, so that you'll have a separate program to demux, and/or convert audio files to MP3. iSquint doesnt allow for much customization, but like Videora, its simpel and gets things done.
Video Playback:
Download VLC because it plays almost all your video files with accurate timelines. Also, there will be some WMV3 files you cant watch with Quicktime AND VLC, so use iSquint to convert them to a viewable format.
Chatting:
I found chatting to be wonderful on iChat, am going to try Adium.
Photos:
You know that feature on Windows, where your .gifs will automatically "play" in their thumbnail forms? Well, you're going to miss that simpel feature in Mac, cause it doesnt do that.
There are some programs out there that is very useful, but you have to pya.
Overall, my experience with the osx as my main computer is this: Its great but lacks some things. Something that really annoys the hell out of me is iPhoto. People praise it, but I dont know why! Its orginization is an effin MESS! They all get seperated by dates, and than by more dates, and than by more dates! If anyone could tell me what to do, it'd be great! Not only that, it separates it by thumbnail, and original! Ugh. What happened to the simple days of adding a photo to the folder you want, and thats it. I feel like there are a bunch of duplicates I dont know about roaming in my harddrive somewhere.
Also, while using Photoshop, everytime I save, it saves it as a "Photoshop Jpeg" or somehting. And it isnt recognizable by some websites like Photobucket, Myspace or Facebook! I would have to send it to my firend's MB (because he doesnt have photoshop), use his MB to upload the pictures for it to work!
I also miss a packaged paint program, anyone have any suggestions?