Should we adopt this aussie??

Question
Hello Anne.  Thanks in advance for your help.  First a little background.  My husband and I are anxious to adopt a new puppy.  We had a 14-year-old Sheltie who died 8 months ago whom we loved dearly. She was just the sweetest dog ever.  Our house just hasn't seemed complete without a dog running around.  We probably would already have another dog by now except for the fact that we would like to adopt and we just haven't found the right one.  Or else, if we think we have found the right one, apparently LOTS of other people think it's the right one for them as well, and so we have not been swift enough or lucky enough to "beat out the competition".  :)  We gave some thought to getting another Sheltie, and hadn't ruled it out, but were also giving a lot of thought to getting a slightly smaller dog that would be more of a companion animal.  (Our Sheltie grew up with our daughters around which provided her with lots of activity, but they have since moved on to college and so are not living at home now).  We were also wanting a dog that would be friendly - to family members as well as acquaintances and children, since we see grandchildren in our future.  Now for the question.  We were at a Petsmart yesterday that was having a large adoption event.  Among the dogs up for adoption were two 9-week old Australian Shepherds, a male and a female.  These puppies had been hand-raised since they were 3 days old.   (Their mother was apparently very young and had refused to feed them after that point.) We fell in love with the female.  She was VERY sweet...she was much calmer than her brother and liked to snuggle in our arms.  We remembered watching a show about testing puppies for temperament by seeing what their reaction was when you cradled them on their back and when you held them up in the air under their arms.  When we cradled her on her back, she wasn't the most comfortable, but she didn't really fight it (unlike her brother!) and when we held her up under her arms, she would just hang limply.  We interpreted both of these reactions to mean that she might tend to be an easy-going type of dog.  Would you agree?  Neither of us has had any experience with Australian Shepherds.  Could you give us an idea of how you would compare them to Shelties....a breed we are familiar with?  I suppose one of my biggest concerns is the amount of exercise they require.  Honestly, what I have read about them in this regard scares me.  However, while we were at Petsmart holding her, several people came up to us and talked about what WONDERFUL dogs Australian Shepherds are.  Most either had one currently or had had one in the past.  None of these people struck me as they type that spent 2 to 3 hours a day out running with them, but I could be wrong.  We paid the adoption fee for the dog.  However, we were not allowed to take possession of her until she was spayed which will be later this week.  I just want to make sure we are making the right choice while there is still time to change our minds.  If you have any thoughts on our situation, I would really appreciate it.  Thank you so much.

Answer
Aussies are very, very active dogs, but can be kept busy with interactive toys, food puzzles, frisbees and tennis balls, if you don't have cattle;-))  I just bought a tennis ball launcher for mine (Go Dog Go).  The most important requirement is that they must be EXTENSIVELY socialized as young ones, and through adulthood, so get the pup in to a positive training puppy class (one that uses clicker training, and has off leash puppy play is best) as soon as you get her!  Take her everywhere and let everyone handle, meet and greet her.  She should see all these things before age 12 weeks: men, women, babies, toddlers, kids, goofy looking teenage boys, dogs, puppies, different surfaces, elevators, revolving doors, umbrellas, cars, hats, sunglasses, wheelchairs, walkers, hula hoops, cats, old people, etc. (you get the picture - EVERYTHING you want her to accept when she is grown).  Sit outside your local post office on Saturdays and let people give her treats as they walk in.  Take her to the vet and groomer and just walk in, get a treat and walk out.  You'll build a dog that isn't leery of going there.
Read this: http://www.avsabonline.org/avsabonline/images/stories/Position_Statements/puppy%...
If you train early, you will have a smart, wonderful companion.  Keep going to classes beyond puppy class, and think about going to agility class, or doing some other fun activity with her - these dogs need a "job" but it can be fun for you, too, and doesn't necessarily have to be livestock herding.  If she is "herdy" then you will need help to train her only to herd appropriate things, and not kids lol, just as you would do with a Sheltie.  But, if you get in with a good clicker trainer, that should be a breeze.
Start immediately teaching her to recall to you.  I use this method, and my Aussie has never failed to come when called, even off livestock: http://www.cleanrun.com/index.cfm?fuseaction=product.display&product_id=440
There are some great training videos at Dogmantics or on the Kikopup youtube channel.
Someone once said, "I asked God for a friend - he sent me an Australian Shepherd."  This will be a lot of work, but these guys house train quickly and are awesomely smart.