Good support for documents, new browser and a newer mypaint.

Besides what is said above me:
The newest sympy + plot modules
the IRC client Irrgu: While XChat does it job great, I always liked the interface of irrgu more, was more native looking and designed for maemo 5 specifically.

Edit: Earlier version of midori with specific maemo 5 looked great too, except that the engine was broken (https doesn't work)

A good maps application that does offline routing too