I have found myself unable to use MIDlet icons properly on S60 3rd edition. The 3250 reduces a 42x29 icon to some mushy pixel mess barely 15x15 pixels in size. Icons that have no file in the jar lead to graphics glitches in the GUI.
Also, I have problems using a network connection - the "do you want to allow the connection" dialog appears, but the "choose your connection" dialog is HIDDEN BEHIND the application and doesn't react until the app is closed. Only very rarely it appears as intended. The only thing I'm doing is animating the screen while waiting for the connection to be established. This happens both on Gamecanvas and Fullcanvas.