Not seen that issue but that is not to say it is bug free. I do a fair amount of colour work with it and mostly find a way to achieve the result I want.
I don't have a problem with the UI but I haven't used anything else except Snapseed and Picassa. It did take some practice to get into it, particularly coming from an "instant fix" environment to filters, layers, masks, overlays and what have you. I appreciate the versatility these days but there were frustrations along the way.
A V2.0 that needed paying for came as a bit of a surprise. Previous upgrades had been free-of-charge. I do wonder if paid for updates will become more regular, after all it is a business and repeat income must be very attractive to them.