I'm also thinking of the Kaiser after returning the G900.
The screen is great but there are some things worth remembering:
1) No matter how good it is, it's not much use if you can't see it outside, it's a mobile device after all and that to me means in or outdoors use, but the G900 is indoors only. Believe me in bright daylight it's a struggle and in sunshine you can hardly tell if it is on or off.
2) Windows Mobile 6 doesn't run at the panels native resolution (it would be unusable if it did see point 3) and so is scaled bigger, so when in Windows Mobile you are getting the same amount of information per screen as you would with a 240x320 resolution. The ratio of the G900 means you end up with a bit more vertical space, but not a lot of difference.
3) When using anything that takes advantage of the G900 resolution, i.e. remote desktop or viewing a web page at 100%, while everything is pixel perfect and sharp, text and images are so incredibly small I felt like I was going cross eyed after a few minutes of squinting at the screen. You'd struggle to read anything on the move at that resolution and certainly couldn't outdoors in daylight.
4) The screen measures 45x65mm, I'd recommend cutting out a piece of paper to those dimensions just to visualise how small that screen is. Most pictures you view on your computer of the G900 will see the screen larger than real-life so it's a bit misleading when you screen shots.
Taking the practicalities into account of just how usable the G900 resolution is, and realising the screens outdoor limitations and it's tiny size making anything running to take advantage of that resolution migraine inducing, I can understand completely why the Kaiser is still 240x320, it's a practical resolution for a tiny display.
The money saved on the Kaiser by having a sensible resolution means you get a lot more extra elsewhere.
If the G900 had a 240x320 resolution, would anyone show any interest in this phone for it's other features?
The G900 also has reliability issues that may or may not get satisfactorily fixed.