There hasn't been a better time to switch.

I have been using PC's for 10 years now, I work on them all day. The last time I had used a mac was about 6 years ago in graphic design, I never even thought of switching from my PC to a mac until just recently.

Portability: The 12" model is definitely portable and light, I would definitely recommend it over the larger model iBook.

MEMORY:
256MB of memory is sufficient but I would definitely consider buying this model with more memory.
Upgrading from a 256MB model afterwards will force you to buy a new memory chip and discard your 256MB chip because there is only one memory expansion slot so it is something to take into consideration when purchasing.

PROCESSOR:
800Mhz G4 processor packs a good punch, it seems very capable to handle any tasks I throw at it. If I had to do it over I might consider a model around 1Ghz.

HARD DRIVE:
30GB hard drive is fast enough however, I find myself filling up this drive very quickly, I think it is the biggest downfall for the model I have, I see myself frequently backing up my data and removing it from the hard drive for more space.

CDROM:
CDRW/DVD Combo drive, I think the Combo drive is essential, being able to play DVD's on the go is great, and being able to burn CD's wherever I am is an invaluable tool.
This drive burns CD's faster than I expected, I was impressed. I love the slot loading drive over the tray loading, I've always found myself hitting tray loading drives and feeling as if I was going to break the tray off.

SPEAKERS:
Notebook speakers have never been known for greatness, the iBook's speakers are no exception to that rule, though they are good sounding. I have cranked up some music using them and I didn't get any distortion, the sound was crisp and clean. Overall good notebook speakers.

VIDEO:
32MB ATI 9200 video is pretty good with a native res of 1024x768 should be capable of handling whatever you throw at it, if your going to do anything more intensive, moving up to a powerbook may be what your after.

DISPLAY:
The display is bright and crisp, it looks excellent. I did use the OSX color adjustment because it was a bit on the bright side and that helped out a great deal, nicely saturated colors, crisp fonts, couldn't be happier with it.

MODEM, 10/100 ETHERNET, FIREWIRE 400, TWO USB 2.0, VIDEO OUT, HEADPHONE JACK.

Built in modem and Ethernet and firewire is great.
Plugging into my home network was easy, I just plugged in the cable and I was set, I didn't need to configure a thing.
Two USB 2.0 ports work very well, I sometimes wish it had 3. The Video Out port works great for connecting to a monitor quickly and easily.
The headphone jack works well too, the quality of the sound is good.

BATTERY:
I haven't used the battery to a point where it has gotten very low. Apple states you can go 6 hours on a charge. I've only used it for a couple hours at a time on a charge and it seemed to have a good amount of juice left.

For those of you where Windows isn't essential I would definitely urge you to go to an Apple store and take the iBook for a test drive. For someone who is looking for a change I think it is an excellent value and a great place to start.
Even if you do have many applications that run in Windows, give Virtual PC a try, running your Windows apps on this machine is a must for someone who is coming from a PC based world.