I recently spashed out and got myself a Samsung i900 Omnia phone. It's the first smart phone I have owned and although I had read that smart phones were buggy I hadn't realized quite how buggy they really are. This page lists the problems I have found and the work arounds. It also covers those things that I think should be on page one of the manual but seem to strangely be missing from it.
Black Screen Of Death
The phone switches the screen off and then never comes back on. It's unresponsive to tapping on the screen or pushing of any of the buttons (even the power button). The only way to bring it back to life is pushing the reset button on the top.
I've read up on this one and it seems to be related to the Samsung widgets that can be placed on the Today screen. My phone came with "Samsung Today 2" switch on by default and suffered badly from the Black Screen of Death. Many people have reported that the "Samsung Widget" also causes the problem. Since I switched to "Samsung Today 1" (to give myself a little more space on the Today screen) I haven't had a problem.
Accelerometer Not Working
The accelerometer just stopped working 48 hours after I got the phone. I haven't got this working again yet. Under Settings > System there is a Motion Sensor option which can turn the sensor on or off. Mine is switched on but still not working - I might be sending the phone back.
Update: I plugged the phone into the USB connector and went to the Motion Sensor control screen for the hundredth time and checked the vibrate on rotation option then pressed ok and it started working again. I don't know if the USB lead had anything to do with it, I suspectd not. One idea that has come to mind is that it might be related to the fact that it is very very cold in our house at the moment (<10 deg C) because we have no heating and it's nearly winter!
Backlight Not Switching Off
The automatic back light switch off is very unreliable. It is not uncommon for the back light to be on all the time that I am on the phone even though the settings indicate the back light should go off 10 seconds after a call starts. I also noticed that the back light was staying on when I put the phone in my pocket. This one is missing manual option, press the power button to turn the screen off. I suppose that it's impossible to detect when the phone stops being in use when it's bumping around in a pocket. I also haven't found a useful automatic screen lock to protect against accidental presses. The manual option of pressing and holding the call end button seems to be fairly reliable though.
Volume Too Low
The volume of the speaker and the headphones is, by default, far too low. Fortunately there is an easy work around to this one. Dial the number *#0002*28346# and you will be presented with a volume control application where you can tweak the various settings. Caution: don't set the volumes too high you can damage the phone (and possibly your hearing).Once you have tweaked your settings you need to select apply from the bottom left menu or the settings won't take. More information can be found here: http://www.modaco.com/.
Opera Limited to Three Tabs
I use tabs like they are going out of fashion and to only get three under Opera is a real pain. It turns out that this isn't actually a bug as such it's just a setting that is "wrong" but easy to fix. Open Opera and enter "opera:config" in the address bar (without the quotes or a http://). This will bring up the Opera configuration application. Search for "tab" and change the setting from three to nine. You will have to restart Opera for this to take effect.