For example, currently, many Filters don't have previews (Or the preview window is too small), which make apply them become a slow try and error game.
Also, the Text in the picture can be hard to select, as sometime you mistakenly select the underlying layer instead of the text.
Also again, Filters cannot be directly applied to editable text. Sure, GIMP will convert the rasterized text back to editable text, but doing so will discard all the applied Filters.