[Tilt, TyTN II, MDA Vario III General] ASCIIker:
you might also want to define what a "problem" truly is in your opinion...as well as assess your own capacity to deal with "problems" and your commitment to dedicating some time to investigate, research, and find solutions to the "problems" (unless they turn out to be hardware issues).

the kaiser is my FIRST winmo phone and i've had it for 1.5 years now and it is a joy to use, provided you're willing to invest time and effort in reading about the possible tweaks and customizations.

most of the "problems" as stated above are due to user errors...i also include in this category problems that stem from unsuitable radios for your area and/or ROM. although the official ROMs TRY to ship with a radio that SHOULD give you good reception and data speeds and gps performance and battery life, still some people get better (and sometimes worse) experiences after they swap the radio versions.

the camera is great until its transparent plastic cover on the back panel gets inevitably scratched (takes about 4 months of use if you're not using a carrying case). the workaround for this issue is to remove the back cover and then take a picture/video if capture quality is a preference. the camera is autofocus but always seems to be locked in "night mode" and this equates to low FPS when shooting videos. the workaround for this is to run the camera app, put the device in standby, cover the lens with your palm, and wake the device. you'll get smooth FPS at the expense of a darker image. hope you are starting to see how the community has developed/discovered acceptable workarounds.

the stock ROMs tend to have a lot of bloatware (there are workarounds for preventing the bloatware from being installed on initial setup after a hard reset). the stock ROMs are generally EARLY builds of winmo6.0 and winmo6.1. to stay on the bleeding edge of features and performance, you're left with no choice other than the superb cooked ROMs available here on xda (including the much improved winmo6.5).

if you're already eyeing the polaris and you are satisfied with its features and reviews, the kaiser is essentially THE SAME DEVICE with slightly different looks, a d-pad, a tilting screen (available on only ONE other htc device, i.e. the LATEST touch pro 2), a slide out hardware keyboard, and an easier mechanism to hot swap your micro sd card. incidently, these advantages make the kaiser more popular (than at least the polaris) and this gives it a lot of regular attention and lovin' from the fine chefs and developers at xda.

usb port failures are common, but i gather a lot of other device families from htc suffer from the same problem.

last but not least are the issues related to the video drivers. once again, the polaris suffers from THE SAME video issues. even most of htc's NEWEST devices still have shoddy video drivers (probably qualcomm or at least htc's technology deal with qualcomm is to blame). once again, work arounds and tweaks and community developed drivers are available that manage to achieve an acceptable level of video playback performance, 3d rendering performance, and general GUI operations for most common use cases.

the final set of issues are probably due to WINDOWS itself. the kaiser has a regular 2.8 inch screen and this is not the best size at which winmo6.0 and winmo6.1 can be finger friendly. winmo6.5 is a LOT better at being finger friendly even on a 2.8 inch QVGA screen like the kaiser's (and the polaris'). and don't forget, nearly ALL the devices upto and including the kaiser (and even the newer diamond and touch pro 1) have ~2.8 inch screens. again, some applications are DESIGNED to be finger friendly regardless of the OS version, and tweaks and add-on applications are available to improve the size of the keys on the dialer and on the on-sceen keyboard, for example.

THAT, my friend, is the whole deal. every device has its own personality and thankfully, most of the kaiser's issues have (both easy and kinda tricky) workarounds. the rest is up to microsoft to quickly evolve winmo6.5 to be rock stable, fast, and (nearly) fully backward compatible with the rich base of software available for the windows mobile platform.