We recently updated a client to DW10 from DW9. He's complaining that searching for images in the Assets section of the Admin UI is considerably slower than it was in DW9 and I've confirmed this to be true. The search is very slow when you navigate to a subfolder (Assets>Images/ProductImages) and search from there. The client keeps most of their product images in this folder and it contains around 200 thousand image files. It's quite large but in DW9 the search / list rendering is much faster.
Best Regards, Jóhannes