As soon as I bought the iPhone 4 I also got the Speck – Darkest Tartan Case for it and was amazed by its sturdiness and fit. I also really liked the textured back side of the case aswell as the rounded corners, it made the iPhone much more comfortable to hold and also easier to grip when picking it up.
To my great disappointment though one day the top side had cracked without any apparent reason (I bet they get to hear that every day! But it’s true!). I contacted their support and in a quick reply they just told me to send it in, which I did. Thought that it was going to take ages since I am also based in Sweden and had to send it to the US, but two weeks later I got a new one in return. Thank you Speck! (make sure you check out their products at speckproducts.com)