I just finished my first upgrade to GP2015 (in our internal billing system) and I thought I'd jot down the required steps
- Upgrade the app to .NET 4.5.1
- Install eConnect for GP2015 on the dev machine. I always uninstall GP2013 at the same time
- Set references to the new 2015 eConnect dlls
- Drop and recreate your Service Reference
All done.
If anyone needs more details on any of those steps, please let me know.