First reported in Apple iPhone 4, "death grip" can muffle the wireless signals of the phone it's held in a certain way (like in landscape mode).
Got my hands on HTC Sensation a few days back, and came to know how the phone can actually get a noticeable signal loss even when the Wi-Fi speed is pretty decent. Watching YouTube videos in portrait mode was a smooth experience, but the moment I switched to landscape mode and clicked on a video, all I got was a lot of buffering time.
HTC's back cover could be the reason behind death grip. This removable cover is made of metal but there are plastic areas in between to work as antennas for the phone. If your hand by chance covers these plastic pieces, the result would be a drop in the signal receptivity of the phone. You might face the death grip problem while browsing Internet on Wi-Fi, Bluetooth connectivity or when you are listening to radio.
If we keep aside the problem of death grip, Sensation is a good phone. It feels great in hands and I must appreciate the bright display of the device. For more specification, videos of the phone or in case you want to buy it, check out this link: