To reproduce:

1. Have any project open.
2. Have collab or services windows open.
3. Resize collab and services windows fast.

Expected result: No latency or delays are visible on the windows, Unity editor refresh rate is same as collab and services window refresh rate.
Actual result: There is a delay, window frame gets drawn first, the collab/services window content gets refreshed only after 50/100 ms delay. Doesn't look like high quality product.

Reproduced on: 5.3.5p8, 2017.2.0b9 (95ec3a4d5d9d)