As a 20 year Minnesota resident and Vikings season ticket holder I will weigh in on this issue.
Point #1: As romantic as the "football is meant to be played in the elements" and "home field advantage" ideas are they will never be able to overcome the underlying thread that drives all NFL owners. MONEY!
The reason the Vikings are seeking a new stadium is money. The three main things the Metrodome can't supply are:
A: Parking revenue (all lots are owned by others, including a large amount by the Minneapolis Star-Tribune)
#2: Club seats (these are seats that have all the amenities of a suite without requiring having 20 people with you) they are typically around $500 apiece.
D: Upgraded concessions to sell you different stuff at three times the normal price compared to the regular stuff at three times the normal price.
In order to get more money the Vikings need to extract it from the people that have the most of it (i.e.: corporations, wealthy people with disposable income (of which the majority are older), etc... The amount of corporate owned QUALITY (between the 20's- lower deck and first 10 rows upper deck) season tickets is staggering. I am in the 25th row on the 32 yard line and of the seats within 4 rows in front and behind and 10 seats in both directions (appx. 250 seats) I see roughly 60-80 familiar faces each game. When I ask the non-regulars where they got their tickets they tell me they were given to them through work (70%), given to them by a relative or friend (20%) or scalped (10%). Let's face it, corporate big-wigs, old people and fringe football fans do not want to watch football in 20 below wind chills, much less spend $16.95 on a turkey freschetta delivered to their seat. If the new stadium was open aired they may be able to keep selling out but there would be a lot of empty seats in a non-playoff year December game not paying $30.00 for parking or drinking $7.00 beers.
Point #2 - The 1.5 Billion complex will not be able to survive on 10 dates a year. They need a roof to attract concerts, monster truck shows and religious conventions from late Oct - early April. Being able to say a summer concert will occur "rain or shine" is just a bonus.
Although I have no major qualms with the Metrodome as a football stadium (except for a lack of bathrooms) and that it will add 30 miles to my drive (I believe the proposed site is 15 miles north of downtown Mpls) I hope this project goes through because it will guarantee the team will stay in Minnesota. And as a bonus it will have occured without Billy Joe "Red" McCombs making a penny from it.