I dont like hiding my ip4 in any case, because its so beautiful, especially the steel rim.
Thats why I use a sleeve. The sleeve I have is actually for an iPod touch, but my ip4 fits perfectly in it. Its a black leather Belkin sleeve and it was only $9.
Since I have a sleeve, it gives me the ultimate protection when its inside the case, and when im using the phone, I make sure I have a solid firm grip and im aware of my surroundings.
Vibration even works perfectly when inside the sleeve because its so tightly packed.
I dropped my phone like 3 times when inside the sleeve, not a scratch appeared because the leather was so smooth and bouncy. The drops were about 4-5 foot drops.
Heres what it looks like:
http://www.daydeal.com/files/i11/f8z362.jpg