Yup, I have that problem too. But its as pronounced as indicated in the picture. It is pretty obvious though. It looks like the 'spring' is too stiff causing the buttons to be lifted. It is only on one corner though (the home button).

Another problem that I find very annoying lately is the automatic connecting to Edge/3G networks for no reasons. I don't know if it eats into my bill but so far the 'unbilled amount' on my account is pretty low so I presume it does not affects me. I learn that there's a patch to disable this connection but can I reverse this as easily like a flipping on and off?
In my opinion, the Touch Diamond is probably the most popular and desired PDA gadget phone released by HTC among young users and enthusiasts to date. Not necessarily the best selling. For one it is highly priced and is positioned as a premium high-end product. Generally not many people would want to spend that kind of money on a phone. However, Touch Diamond has managed to grab a lot of media and press attention on the internet. And these stir up the desire and the perception of a very successful product. Advertisements and forums works wonder in marketing. Hehehe!

However, 30+ users and counting is very good considering it is a premium product. If you ask me what is HTC's best selling PDA phone, I would nominate the original HTC Touch and in the near future, the upcoming entry level replacement of the original Touch.