Is this one of those cases where sometimes one tool gives a better result on certain shots than another tool? I’ve had shots that I have managed to get working Flame that haven’t in Syntheyes. I’ve also found Nuke’s camera tracker to do the job when Syntheyes hasn’t worked as well. But I predominantly use Syntheyes with Flame.
Anyway, a left field 3D tracking solution which has an awesome support community, lots of tutorials and ways to create a whole lot of bits and pieces for your post 3D track comp would be Blender. I haven’t used it yet as I haven’t had a need to but I’m planning to give a try. There are heaps of ways to manually adjust the track on a problem shot which I like (it’s not a set and forget solution as simple as Syntheyes) but if you really need to spend a lot of time getting a track right then I think it has the tools to be able to do it. I love the idea of Blender, and have used it for a couple of incredibly basic modeling jobs (buildings in background) and I liked it. Whether or not it is a practical solution is another thing though.