any issues on upgrading from 11.0.13 to 11.1?

[Kyne]

Hello fellow Cognos Analytics gurus,

We have just upgraded our Cognos from 10 to 11.0.13 and tested every reports that work perfect now.
with new data module and dashboard introduced,
We have found that current data module and dashboard are quite limited to meet our business needs.

According to the new features on 11.1 from Cognos,
It looks more promising for data module particularly with custom SQL support and dashboard with data format update.

a bit of long background but before we go ahead,
I'd like to gather some information that i should be aware of to upgrade the version.
I understand it'd be not easy but absolutely grateful if you can shed some lights on the below questions.

1. any issues on reports working on 11.0, but not working on 11.1?
2. do FM packages need to be re published from 11.1? or simply 11.0 packages are re usable?
3. IBM says the installation would be an 'over the top' upgrade, not installing from scratch. does it mean that any configuration or data connection setting will remain as the same?

We are running like 600 reports and it'd be not our go to if we have to test all those from scratch one by one even though our option will be
more narrowed down.

Thanks in advance for any advice or sharing on this topic.