Invisible Fences?

Question
I have a 3 year old Aussie mix. I went with an aussie mix after months of breed deliberation and a decision that I wanted an aussie, but that a pure-bred may not be a good introduction to owning the breed. She shows a lot of very aussie traits: she is very protective of me, very eager to learn new things and impress, wary of new people (though we have worked with trainers and she no longer nips and will - unhappily at first - let a new person pet her in most situations). She listens very well once she trusts someone UNLESS that person asks her to do something that would cause her to seemingly disobey/ disappoint me, or to walk too far away from me if it doens't appear I'll be there when she returns. She currently living with my two roommates and their two dogs in a house with a huge back yard and woods to play in with one dangerous road on the other side of the house. She is VERY well trained with roads as we lived in a city when I brought her home. I usually sit out back with her and the other (also well-trained) dogs for a few hours a day, and my roommates and neighbors will let them out if they are going to be out back also. A good friend has offered us an incredible deal on an invisible fence (her parents own a great pet store) and my roommates are excited. Training Kyla on it makes me nervous. While she is an unbelievably intelligent dog and a fast learner with recollection of some crazy tricks and fun things; I don't know if she will understand it is for her safety from the road. I'm almost afraid it will make her more likely to take off (and not hurry back?) when I am not home if someone startles her. I don't think I'd ever plan to let her stay out with it unless someone was still outside with her anyway (as it is now). The road is dangerous. . . and a real fence would restrict her from the giant play area she is allowed now. (We also rent here, she had a privacy fence at one residence and did not really enjoy it unless I was outside with her anyway) Not necessarily looking for an answer, just some insight to enhance my decision. Even if we get the fence for the roommates, I may not train her on it. Thank you!

Answer
Aussies are one of those breeds that are often "one trial learners" = which is great if they learn what you wanted them to, or thought they were going to.  However, some Aussies, exposed to a shock collar (don't sugar coat it, that's what it is) will learn to be superstitious of going into the yard at all.  Other bad stuff has happened because of these systems, and I think you must have a thorough knowledge of that before you ever decide that this is the solution for your dog.  By the way, deer fencing is nearly invisible, you can teach your dog where the boundary is, and it's relatively inexpensive, too, to do a large area with it. (Also portable.) They do market a type of this fence for dogs (www.bestfriendfence.com) but check out the farm supply to see if you can get it cheaper.
You might want to read the information at these sites.   
http://www.hollysden.com/say-no-to-shock-collars.htm (there is a special section on fences, too)
http://www.joelwalton.com/shockcollars.html
Personally, I would never use a shock collar on any of my dogs for any reason. I'd rather drive to the beach every and throw a frisbee than do that to my dog and risk her not learning the right lesson, losing trust in me, or worse, developing aggression toward anything that she sees on the other side of the fence at the time of the zap.  JMHO, but I hate the things.