Jared Allen, Pat Williams, Kevin Williams, and Ray Edwards make up a disruptive, devastating unit that rushes the passer and smothers the run. The pass rush has been much less effective on grass than on turf, but this is still a unit that can wreck an opposing offense and cover for deficiencies in the secondary.
Is there an NFL team with skill position talent that you would prefer to the Vikings? They have an elite RB in Adrian Peterson, a good red zone TE in Visanthe Shiancoe, and a diverse group of WRs in Sidney Rice, Percy Harvin, and Bernard Berrian that provide deep threat, short threat, runs after the catch, and basically any combination of things you'd want from WRs. Certainly having an elite QB to utilize the talents of those players brings out the best in them, and the Vikes will need at least mediocre quarterbacking to get to the playoffs. But remember 2007, when the Vikings' top receiving threat was Bobby Wade? Those days are long past.
I think the Vikings might need to get creative offensively: there are some things they can do with Jackson, Peterson, and Harvin in the backfield that could really electrify the field. It's also evident that if Jackson is again the starter, the focus of the team leans more on the run, so the run blocking of the offensive line will need to be more effective, and Toby Gerhart will need to provide something on 5-10 carries a game.
What do the 2010 Vikings do without Brett Favre? My guess is they eke out 8-10 wins, lose 2-3 games that they should have won, maybe get into the playoffs, and in the playoffs probably lose, but with matchups and luck, who the hell knows. The strengths of this team are enough to make them competitive any week (as has been true for most of the Childress era, actually), but the weaknesses (serious questions about the quarterback and the secondary, for starters) probably prevent them from being an elite team again. But I'll hope, because it's better to cheer with hope.
Two nights ago I had a dream that the Vikings started out 2-0; in particular, Pat Williams was just running around crushing people. For you, dear reader, I'll put my crazy purple optimism on once again. We'll get through this season together.