My thought on that is that the IRS is scared that they won't be able to criminally charge every tax protestor if there ever gets to be a ruling by a federal appeals court that goes against them in one of these cases... so when a guy fights enough they just let him slide in a manner that creates no precedent.
You have it right here. The IRS withdraws often at the last minute because they know they will lose. There are many many cases which would have been wins if the IRS had not run away.
In this case, Cryer is a gold medal trial attorney. The IRS brought in their big guns, tried to taint the jury pool, tried to bar evidence and statements, tried changing the argument attack and throwing in distraction after distraction.
Cryer beat them because he is experienced but he said that others without his trial experience would have been beat.
And yes, the Income tax as applied is unconstitutional.
If you have a high speed internet connection, study this film (easy to watch):
http://video.google.com/videoplay?docid=-1656880303867390173