how long did it take you guys to upgrade/migrate from 7.1.2 to v8?
About a month. This includes the 8.0 installation, DB components installation (nightmare), migrating the Application code and testing the code. I did an upgrade for a client not long ago from 6.1 to 7.1.2 and compared to that this migration was fun, easy and quick!
Did you upgrade on top of v7.1.2?
No, we did the upgrade in parallel. We were supposed to get rid of our old boxes (hosting WM) so we started with a fresh install on the new boxes.
How long did it take for you to replace MIS to more of a web services solution?
We started using web services from 7.1.2 itself and did not have to do anything new in 8.0.