I bought full session tickets for DSM through a friend the day they became available sometime last year, and plan to attend every game for sure...whether Iowa is there or not.
I did the same thing the last time the Metrodome hosted 1st and 2nd round tickets (when Fizer and ISU played there). My experience was that there were scalper tickets available, especially for the 2nd round after teams are beaten in the first round. There will be tickets saved until the teams are actually announced for the region, and then offered to the fans/season ticket holders for those schools. But when people fly in for the weekend and their team loses in the first round, a lot of them want to dump their tickets for the rest of the games and leave town.