Upgrade Windchill 9.1 to Windchill 10

We intend to upgrade Windchill 9.1 to Windchill 10 and wish to hear if someone done it already.

Our current version is 9.1 M060

We have 4 replica sites.

Do you have any tips?

What type of problems you encountered?

How long did it take?

Any insights would be greatly appreciated.

Thank you in advance,

Tami