Reproduction steps:
1. Create new Unity project
2. Add scripts from https://docs.unity3d.com/ScriptReference/Handles.FreeMoveHandle.html
3. Create new GameObject
4. Add script "FreeMoveHandleExample" to the GameObject
5. Try to move the white square

Expected: the white square should move with the cursor
Actual: the white square lags behind the cursor

Reproduced on: 5.5.6f1; 5.6.5f1; 2017.1.3f1; 2017.2.0a3

Note: reproducible only in Retina environment

The issue is fixed in 2017.2.0a4 and higher versions.