Today, I read the GtkSourceview 1.90 release announcement on gedit-list. After having finished my math excerises much earlier then expected I decided to hack GtkSourceview2 support into Gobby. I committed it a few minutes ago into SVN, after having received some advice from Yevgen Muntyan to get it to work (You have to associate a style theme by hand to get highlighting, which will hopefully be changed in the future so that a default theme is used if none is given).
GtkSourceView2 basically comes with a new syntax highlighting engine that allows embedding languages into others (such as JavaScript into HTML, as shown on the screenshot). It also has theming support and mapping between filename patterns and language definitions, which Gobby had to implement before (and it still does since GtkSourceView1 is still supported).