I've had a 2 part epoxy floor installed now for 8 years and not one area has lifted or cracked.
I used the etching method with acid and rinsed while etching and then power washed and then power washed again. Then scrubed and power washed some more.
It really is all in the prep, if you skip or think "that'll do", then I think you'll have problems further down the road.
I really wouldn't go the grinding method unless your floor is covered in grease or bad contaminates. The etch really only just breaks the fine surface particles and leaves basically an 80 grit finish. I can't imagine how this would effect a fiber reinforced concrete.
Good luck, as it'll all be worth it in the end.
Here's a link with some photos of my garage floor -
http://forums.pelicanparts.com/porsche-911-technical-forum/231795-garage-floor-paint.html