I have GelaSkins on my iPhone and also on my Kindle 3. They look really nice if you apply them correctly (I managed to install mine just fine, though the youtube videos made it look exceptionally hard).
However, I prefer them much more on the Kindle as its a bigger device and also, less prone to needing too much protection.
I used the iPhone with just the skin for a few days, then gave up and started using it with the skin AND a case. So not really worth it, IMO, if you want protection.
With the design of the DHD, I feel the skins are useless as I would always be worried about the Sim cover popping off if I used it naked. I use it with a silicon back cover and am happy.
Overall, save your money
Current Phones: SG Note 2, Moto Defy Mini, Nokia 113 + 101
Phones/PDAs: iPhone 5|iPhone 4S|Galaxy Nexus|BB 9900|iPhone 4|HTC Desire HD|BB 9300|Nexus One|Nokia E52|BB 9700|HTC Desire|BB 8900|HTC Magic|Samsung i780|Nokia E71|HTC(Kaiser+Excalibur+Prophet+Feeler)|Axim X30|Nokia 6600|Palm(T|E+Vx+IIIe+Pro)
Gadgets: iPad 64GB+4G|Kindle 3|PSP|iPod Nano 4G Red 16GB|Xbox 360 60GB|Sony PRS-505
Laptops: MBA 11|MBP 13|EEE 901
Photography: PEN E-PL5|Canon Ixus 220 HS|Sanyo Xacti HD700