Firstly this thread is simply to try and help other future users get over the problem I've been having for the past 3 days using Icarus. Also all the posts on Icarus seem to be from 2006 or earlier and I thought something up to date might be helpful.
I'd decided it was time to teach myself some 3D tracking techniques and went in search of some cheap/free programs. Two reasonable ones I've found are Icarus and Voodoo.
Both seem to be great trackers and reasonably reliable. I've been practicing using footage off my iPhone with good results which I think says a lot.
I was getting pretty much perfect tracking results in Icarus, but each time when I imported to Maya everything would be just slightly off. To cut a long story short, after 3 days it was suggested to me by someone to check if my camera keyframes matched the image sequence.
Turns out Icarus (and Voodoo I believe) start keyframing the camera at frame 0, but the image sequence automatically starts at frame 1. Even being off by a single frame makes the whole thing look terrible.
So if you're having slight issues with your tracking, double check that. Hopefully it'll save you several hours work.
Neither of these programs are supported anymore, but for anyone looking for a free 3D tracking solution I'd recommend both of them.
Icarus download and tutorials: http://www.colinlevy.com/tuts/IcarusTutorials/Icarus.php
Voodoo download: http://www.digilab.uni-hannover.de/docs/manual.html (http://forums.cgsociety.org/www.digilab.uni-hannover.de/docs/manual.html)