I'm a bit confused now, not sure which version I have, but either way its not very good...
The cut out is oval and the power/sleep button is very hard to press and unresponsive, the first version apparently have a sleep button that was fine and the cut out was pear/keyhole shaped.
However, mine is not hard plastic as reported on here, far from it. I would say somewhere between hard plastic and silicone. Quite a bit of play and not very hard to get on and off, which has also been reported. Actually I quite like it, it is the material I was expecting having seen reviews of the mk1, i believe this is TPU (maybe a lower quality blend, not sure). I have no issue with the material per-say.
BUT... The biggest issue is that this case will not work with a screen protector, absolutely no way. It's very badly designed in this respect. It's a shame because the design on the iPhone 4 lends well to case designers (cases can attach/snap onto the antenna band) it's pretty easy to have a lip above the screen (so it can safely lie on its front/screen side) yet not interfere with the screen protector. Lazy thoughtless design from Speck, some companies have shown it possible to have a case that does not even touch the screen and some that actually help hold the screen protector down. It's not freaking rocket science FFS.
It also looks really cheap and ugly on the side too where there materiel was injected into the mould, with a bit left sticking out. Looks unfinished. I agree with people who have said this is like $5 Chinese case (in fact i have seen better Chinese cases for less than $5 off eBay, i believe how good my friends is and i think it was $3).
Overall, The HD is a poorly designed case (at least the version i have is). It's obvious that Speck lowered standards to milk their deal with Apple. Certainly not worth retail price, and still useless when free.
Look like it's just going to have to an Incipio Feather for me now. At least I can use a screen protector with it. (Feather + Screen film) > (HD - Screen film). That said, the new SGP Neo Hybrid is looking very good and that may well be my 'forever' case if its as good as it looks. I'm don't know about anyone else, but i am totally sick of trying to find a decent case with no significant flaws, i just want bloody case thats decent... life is too short for all this fuss over a piece of plastic! The original HD seemed to be that case, but this one certainly isn't.