Real good! The best for free!
Reasons for down vote: 1) This simple comparison tool lacks "resync at given line" feature since first request in 2004 (#366 Manual synchronization anchors). Multiple similar requests are already open(#831 Allow manual line alignment, #719 Manual difference alignment, #1149 forced (manual) match or sync, ...). TotalCommander's internal compare has this feature for years. 2) Latest stable release is outdated since 2010 but 297 Bugs, 499 Change Requests and 20 items (oldest from 2005) in ToDo List are open.
Great tool, a bit bulky, resource consuming and slow, those are its weak points, but it does the job fine.