They should fit the HD, however there might be some space in the corners as the HD is rounded a bit more than the regular Instinct. Here are the size specs of the phones though:
HD: # Width 2.3 in # Depth 0.5 in # Height 4.6 in # Weight 4 oz
Instinct: # Width 2.2 in # Depth 0.5 in # Height 4.6 in # Weight 4.4 oz
I'm not sure of the Intensity's specs, sorry. If you know them you can reference the specs of the Instinct in my earlier comments and see if they are close.