I am mostly using GRASS GIS 7.0, which is the development version. Main reason I started to use this version was the better (faster) vector handling. But there are many other new features and improvements.
And the developers keep on adding small and big improvements all the time. Sometimes planned, sometimes as response to an user-request. See here for an example of the latter. Another example where an user request leads to a very welcome enhancement of an existing function is to r.mask.
The function r.mask creates a MASK for limiting raster operation. In the old version, it only accepted raster layers as input, but now it also accepts vector layers as input. See the example below.