I use the Ameda freezer bags. I have never had a problem with air bubbles, breaks in the bag, or leaking. I have about 2500 oz in the deep freeze. These are the most expensive bags out there (about 50 cents per bag) so I freeze 5 oz per bag to save money.
I figured it made sense to use the best bags on the market since it IS liquid gold that I am freezing! I think I have spent about $200 over the past 9 months on freezer bags. That is about the cost of one month supply of formula so, in comparison, that is not too much.
As for air bubbles...I really doubt that one little air bubble is going to cause too much trouble. I personally would not worry too much about that.
Liz