I just picked this game up over the weekend. Yes I have a Wii too. It just hasn't gotten much play since the PS3 has come in. I popped it in and gave it a whirl.
There are lots of excercises, like 30+, ranging from walking to boxing and lunges, each working on some particular muscle group. The sequence of excercises is nicely spread out so you are not constantly working on the same muscles. I only tried to "low" setting which I thought I would breeze through without breaking a sweat. It started off with a brisk walk, then picked up to running. Then a series squats, lunges, curls, stretches, and jumps, 16 excercises in all. The total elasped workout time was 22 minutes and I was toweling off my forehead about 5 minutes in on the 4th excercise.
It is pretty tricky and confusing at first because the way it detects your movement is the way the Wiimote and nunchuck is facing or moving. So you always have to remember to do it in the form that it tells you to, ie. Wiimote pointed forward and starting position and end with it pointing downwards.
My goal is to advanced to at least the medium setting before I get bored of it and give it to the gf.
Oh, also, I don't have WiiFit so I can't compare the two. But my opinion is that EA Active is more "active" whereas WiiFit is more stretchy-balancing.