Is it hard to upgrade to newer OS version?

[dm33]

Is it hard to upgrade to a newer OS version? Shouldn't Android largely be compatible so that you can just take a current build, use the hold drivers and get it running on older phones?
If it is hard, why is it?
If it isn't hard, is there a reasonable process a developer to upgrade a phone to 2.x

 

[oba1]

upgrading is not difficult. there are many guide on the web on how to create custom made ROMs. the problem is drivers - certain drivers have support in the new OS version, and others do not. even cynogen is waiting for drivers to come out - as modding drivers is very difficult and time consuming. stick to cooking your own roms, and installing the new app that come out in a new version over an old rom with the drivers.