The only thing I had to change in the new client was to stop using the black visual theme (under Options => Display) so that I could see the mouseover text for the locked/encrypted, staking, network connections, up to date icons (in the bottom left of the window). When using the black visual theme, the transparency was hard to read.
You should not have copied over the style.qss file.
Delete that one and you should be good.
Thanks for testing!