This sounds like a fairly major increase and, to be honest, it is, however think of what you're getting for the extra £70. You get an extra home game, you get to see the team playing a higher quality of opposition and you'll be helping the club sign better players and giving us a better chance of survival. By comparison, relegated Livingston are charging £280 for first division football!
One major criticism seems to be the removal of parent and child tickets for anywhere other than the Reid Kerr Stand, which is supposed to be the family stand. Seems like a valid point, and it could see folk forced to move stands, pay more or just not go.
With all games next season set to be all ticket, it would be a good idea to get a season ticket. The quicker you get one, the less you pay, so look at http://www.saintmirren.net/content/members/articlepage.php?id=364 for more info.