I purchased my epoxy floor coating from GarageFlooring LLC in Grand Junction. The main guy there is Justin Kraus. He provides good advice and support. I currently don't have the flakes on my floor, but will be adding them soon. The current gloss finish seems to amplify the uneven concrete work in my garage and I'm hoping that adding the flakes will mask this look.
As someone else mentioned, even the gloss-only treatment didn't cause the floor to be unreasonably slick. The only time it's too slick is when I have snow packed on the soles of my shoes. I think it's worse than an ice rink in this situation.
Prepping your floor is absolutely key to a long-lasting floor. The modern solution is to use a floor polisher and a diamond grinding pad. This package can be rented from Home Depot. I used the diamond grinder AND muriatic acid--because I've seen people strip a floor gone bad and it looks like no fun.
Have fun with your project. I've done 4 garages so far. My current garage:
http://www.woodardfamily.com/hosted/Garage.JPG