I've been using Packet Tracer since taking the CCNA classes about 2 years ago, but I keep hearing all the good news about GNS3

. Do you all find it to be much better than Packet Tracer and provide more functionality? Also, I've tried it briefly while at work, but where do you all download the IOS images for it and everything? There's a few weird things I found while trying to use it, like not being able to drag a host directly to the map w/o some message popping up to configure it first.
Not necessarily trying to get direct GNS3 support, but more curious about the experiences from the people who have used it to pass Cisco exams.
Thanks for any feedback.