Even though the tampa 2 appears to be the Vikings base defense, they are deviating from it more this year than any other. As skum mentions, they throw in more man coverages than ever and they will play a variation of cover 1, 2 and 3 at times. The more comfortable Williams and Frazier feel with the back 7, the more you should expect them to mix up the looks they show on defense.
There aren't many changes in the Vikings Tampa-2 system from the traditional 4-3 one gap system. The most important difference is that the nose tackle is tasked with the responsibility of reading the play and reacting appropriately instead of indiscriminately attacking the gap. While you won't see many line adjustments from the nose tackle during pre-snap movement, the nose tackle is determining whether or not to attack the gap or to control it. This reduces the likelihood that the nose tackle will get caught up in traps. On some of these plays, the nose may choose to act as if he's in a 0 technique and attack the center instead of the A gap.
Because the nose tackle is usually extremely powerful and quick in their north-south movements (unlike nose tackles in a 3-4 system, who are not required to be penetrators, but are generally laterally agile), they'll also usually command a double team, which will free up the Mike or the Will linebacker to make the play in the run game. The nose tackle will need to consistently demand that double team in order to make the Tampa-2 effective. This is how the over alignment of the Tampa system deals with the problems of zone-read running endemic to traditional one-gap 4-3 systems, and why Pat Williams was a more important part of our defense than many commentators gave him credit for.
The weakside defensive end is also asked to read the play and will get into contain much more often, instead of indiscriminately attacking the C gap. This means that the defensive end on the weak side is tasked with containing outside runs while the Will linebacker will contain off-tackle and off-guard runs when the weakside end goes wide to direct traffic. The Tampa-2 system in general, and the one employed by the Vikings in particular, is designed to direct running traffic to the Will linebacker, which demands that the Will be a strong tackler more than anything else.
Unique to the Vikings version of the Tampa-2 is the heads up (6-technique) alignment of the strongside defensive end over the tight end. This defensive end will read the movement of the tight end and determine the most appropriate action from there. For example, if the tight end shoots forward with both arms extended, the end will try to penetrate inside to stop the run. There are any number of actions that the tight end will take off of the release, and naturally some of them will be fakes designed to stop the defensive end from making the play. It is up to the strongside defensive end to determine the intentions of the tight end within half a second of the snap. Much more often than not, the strongside DE will still attempt to attack the gap and get to the quarterback while the Sam linebacker will take care of the run or the tight end.