visual diff tools

I usually use vimdiff to find the differences between two files; here are some gui tools that do the same thing:

meld – though version 1.0.0 doesn’t allow line-by-line replacements (I’m told later versions do)
mgdiff – doesn’t allow line-by-line replacements
tkdiff – doesn’t allow line-by-line replacements
kompare – allows line-by-line replacements, but the interface is a bit clunky (in that you can’t easily choose to take diffs from both files without reversing direction)

So kompare seems the best, though none seem as good as Windows tools I’ve used – perhaps time to submit some changes to one of these projects.