Sounds like my experience with Risky Racer, only that when i got employed by Track7 Games, i decided to not continue on that road

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And well, having Emulators means absolutely nothing. Risky Racer (which uses a custom smooth scrolling engine based on completely MIDP1 code - no extensions whatsoever) ran perfectly on all of them. Which is normal really, since most emulators (even from different companies) are the same piece of software with a different skin.
In real hardware (which i didn't had and i was "debugging" by sending binaries to testers, waiting for an answer and repeat) i got all sorts of bugs, including strange stuff like the half screen flickering, movement errors, etc.
At around this point i decided that i won't mess with mobile phone programming until phone companies somehow agree on a format/API/VM (Sun did an awful thing when they decided to not provide a VM of their own but let others create VMs) or i get a warehouse full of different phone models to test on

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Which is how things work actually. Some months ago i met a guy via IRC who was working in a company with the sole purpose of testing mobile phone games. He told me they have thousands of models and they play and finish each game a developer sends to them to all these models in order to ensure that no bugs exist.