I also think I'll have another set of million problems as I have to convert the current database (in latin1) to the new and utf8. This is NOT easy and the docs seems not accurate.
You are correct this is a burdensome task. The wiki describes how to handle the conversion in-place in the same DB version. Last I checked, it did not describe migrating and converting at the same time. I would suggest approaching the UTF8-conversion as a separate task from the Koha upgrade. I'm not sure which order would be best, but I would be tempted to work on the data conversion before the upgrade so that you can identify any problems from that in a version of Koha known to you. Perhaps someone who has done more 2.2 -> 3.0 upgrades can offer their wisdom.... -Joe