I found the omnia 7 a slippery eel of a phone without a cover, so for me this cover serves two purposes; one to make it more grippy to hold (though this is at its grippiest at the sides - the back is actually still quite slippery) and two to protect it from the occasional bump, which I think it will do quite well. The side buttons on the phone are still easily useable, despite not being exposed. It is a nice touch that the case is moulded such that you can feel where the buttons are, and not have to look at the phone.
Would have to agree with the other review here, in that it is not the tightest of fits to your phone. That said, it is far from sloppy and I don't think it will ever fall off on accident.
For the price, you can't really go wrong.