I like it's detail view mode and split mode (two panes). Also when you drag and drop it pops up a menu asking if you wanting to copy, move or link (if you haven't held down ctrl, shift, or ctrl+shift respectively). Good handling of zips and other archives, as well as files over protocols like SFTP. The left-hand panel with places, remotes and devices is handy too.
Would be nice to have something similar that starts a bit faster.
Dolphin was my favourite before I needed to rename a stack of files on copy which Thunar made easier.
/scnr