Hi,
The GPS I would say is average. Some reviewers in Europe rate Kaiser's Qualcomm GPS chipset as better than Sirf Star III. If you need GPS device for daily navigation in Malaysia road, Kaiser can deliver it.
The camera, although it is 3.2 Megapixel is only good enough for outdoor shoot. If you wanna use it indoor, make sure there's enough lighting or else, you'll suffer the lagging viewfinder (slow refresh rate). However, Kaiser has better camera capabilities than most other PDA's camera.
Push e-mail I believe is being used for e-mail with Microsoft Exchange, like blackberry devices. So far, I havent heard any problem with this feature. And sadly to say I haven't try it yet.
System stability is quite good. If you're looking for a Pocket PC running WM6, be sure to check the ram is at least 128 MB. And I hardly encountered system crash, though not to say it never happened before. Keep in mind the etiquette when running WM6 devices, keep running processes as minimum as possible.
The final question is more on build-quality. I have compared Kaiser side by side with Zinc, and Kaiser would have won the build quality test.
Even Dopod 838Pro owner would agree HTC has put in a better build quality for Kaiser.
One gripe with Kaiser is the build in keyboard. Zinc has better. Hope my explanation helps.
And one more thing, the best pocket pc i ever had is O2 Mini aka HTC Magician. Kaiser only comes 2nd.
Ok, right now, I am VERY curious to know why is your best Pocket PC a O2 Mini and Kaiser only comes in 2nd? I had an O2 Mini for about a little more than a year.