I started of in mobile in J2ME and am not looking back, you would want a sizeable portion of the market to even consider switching from the Android/iOS SDKs unless you also have a passion for self harm.

Even something as simple as signing and certification is a massive headache as theres no standardisation of what root certificates are in devices. The UTi and Java Verfied (Java Verfried as we called it) came very close but its still not 100%

No one really upgraded the firmware in their devices and the Java machine could not be updated, when fragmentation issues were solved, it was painful but some useful lessons were learned I guess!