Mine's been working great since I got it in August 2009. But there are three minor issues that I've encountered.
The ONLY real hardware problem I've ever had with the device is SD Card related. I've got a 2GB Class 2 and while accessing my music from it using the Manila (TF3D) audio player it systematically pauses. This is a software malfunction, but it's in relation to hardware.
I also must underclock my SD card when I run a HaRet Linux Application, such as Ubuntu or Android.
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There is also a form function flaw on the Touch Pro 2 Battery case. If you aren't careful you risk the possibility of cracking it near the stylus, mine eventually broke and a small shard snapped off.
When you take the backing off and put it back on you may notice a small bulge in that area. That's where you want to be wary, as repetitively removal and application of the backing will cause this.
Example:
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Last but not least, Rainbow Banding. For some reason the resistive touch screen on the TP2 seems to burn with a rainbow like shimmer if used frequently.
The findings on this are inconclusive but it seems to be happening to more and more Touch Pro 2 users. 40% out of 283* have said their device has had the defect (Including I). I also once read this effected the first Touch Pro as well.
While it does 'burn' itself into the screen you will only notice it at certain angles and in bright lights.
Here's a thread with people claiming to be plagued by this problem.
It contains an example image as well.
I
speculate that screen protectors are insulating the resistive screen and causing it to overheat and burn in-between the plastic layers.
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Other than that, the Touch Pro 2's hardware is superb.