I've noticed a few times that switching tabs causes the gutter to not refresh properly.  Switching to a file with fewer lines seems not to refresh the gutter beyond the number of lines in the new file.

Not sure if this is a known issue.  The attached picture is from a file which has 36 lines.

Also, a brief feature request:  Would be awesome to be able to set the background/foreground colour of the gutter to match the highlight theme :-).  I realise that this could cause problems with images for folding markers and bookmarks, but we could also have options to set images/colours for those too :-P.