I've used Ubuntu Linux for over a year now. Here's my personal experiences so far.
The biggest area where Linux is lacking is gaming. There are some fairly decent games for Linux, but no such plethora of titles to choose from as Windows. But I think if you need to play games, buy a gaming console, because they are designed for the job. Computers are more general devices.
My every day use of Ubuntu doesn't differ that much from using Windows XP. I can surf the web, read my e-mail, listen to music, watch movies and video clips, download software, use an office suite, manage photos from my digital camera, manage my mp3 player, burn dvd's and other cd's, use an external USb hard drive as backup, use USB memory sticks etc.
Installing software is extremely simple when you use the Synaptic package manager and Ubuntu software repositories. There are about 27000 software packages to choose from, and you can also install programs manually if you need to. Mostly this is done with a couple of mouse clicks and that's it. No need to hunt down programs all over the net as with Windows, no troubles with shareware or other limited crippleware.
I don't fret about viruses and malicious programs nearly as much as when I used Windows. I have a virus scanner (you can get it freely from the repositories) and a firewall (running as a default right after installation), but no spyware scanner like SpyBot in Windows. Win viruses can't touch my Linux system.
I have access to some great programs free of cost (the Gimp, Inkscape, Scribus, OpenOffice). in Windows world, you usually have to pay hundreds of dollars for same kind of functionality you can get scott-free in Linux world.
The system is also very stable. I have managed to broken my system only once, and even that was solely because my crappy laptop fan decided to break down in the middle of a big update operation. My laptop got overheated, shut down automatically and while doing that messed up the update oeration, which in turn broke my Linux installation. I had to get the cooling fan replaced.
So far, I've had some individual programs freeze on me, but none of them have managed to freeze my whole system. You just kill the offending program and continue doing other stuff.
And the dreaded command line terminal? You only have to use it in some cases, but about 97% of the time you can do all you need with the graphical user interface. And the terminal sounds more frightening than it is. After all, it is just about typing some letters with your keyboard. Most of the commands you use are simple two-letter things, like "cd" (change directory) or "ls" (list the content of directories or list files). In fact, these two are the commands I mostly use.
You should learn some basic Bash commands and get to know the Linux environment more before you migrate, though. More knowledge is always a good thing and can save you from troubles later.
It is worth the time. After a year of Linux, I find myself to have so much more in-depth knowledge of how computers and operating systems in general work. It just comes naturally when using Linux. It's an interesting, exciting and rewarding OS to work in and to study. Can't say the same thing about Windows. I can't picture myself installing Windows on my machine, ever again.