At my new employer, we use BitBucket, but previously I'd used FishEye. One feature I found useful was a source listing having each line annotated with information about the most recent check-in for that line. This allowed users to see when, for example, a new method was added to a class. IIRC, the left column had a color-coded revision number, and hovering the cursor over it displayed a thumbnail description of the check-in.
Does BitBucket have this (or a similar) feature? The version-to-version diffs are useful, but orthogonal to this use case.