i recently bought 3 cases for my DHD because i couldn't decide which one to get. i got the hydro gel one, a silicone one, and the official HTC DHD leather slip case (product code S550). the official slip case is by far my favourite. bit tight to start, but loosened up perfectly now. really well made, real leather, soft insides, clever ribbon thingy, very nice to use. 5/5
the hydro gel cases are hard plastic and would offer no bounce if you dropped the phone, thereby giving no protection from drops. it also doesnt protect the screen much, and the power button is a pain in the backside to press with the case on. does make the phone better to hold, especially landscape, and would protect the back from bumps and scrapes, but its not a "protective" case. 2/5
the silicone case wasnt much better because the edges were very flappy and didnt feel secure. the bit under the touch buttons flapped every time you swiped the lock screen away. irritating. however it did feel like it would bounce if i dropped it. again, little protection for the screen. 2/5
not all is lost though because il put a bit of velcro on the back of the silicone or hydro gel case and stick the other half to my dashboard, giving me a perfect fit car cradle! this is what i did with my old nokia N96 as well. works a treat. leaves all buttons available, and you just slap it on the dash when you get in the car.