I've been doing some tests with the blender scanline renderer and the Freestyle NPR renderer:
The images rendered here were taken from a wide camera angle, so the model is actually a bit further away from the camera vs the other close-ups I've shown recently. This is important to consider, since the toon line rendering will appear to be wider in proportion to the scale of the model, the further the model gets away from the camera.
In the second image from the left, I've applied a 4 pass HF Sketch effect using the displace modifier, you can see how the silhouette of the model is broken up and will blend better into the background. At this distance the 'painted' effect is less prominent, but this does help to soften the image and blend objects together.
Third up is the 4 pass sketch with the bog standard blender Edge pass turned on. This works ok for models that are close up to the camera, but for objects further away, you can see how the toon lines get ridiculously wide in proportion to the actual model. There's no way to control the line width in Blender (...yet...)
Fourth up, the Freestyle renderer does a fairly reasonable job, with much better artistic control of where lines will go, and a global width control to change the base width of the toon lines for an entire scene. This could be handy for actors who approach the camera, for example, since this control can be animated with an IPO curve.
So it looks like my rendering pipeline will be a layered approach like in my previous productions, with the backgrounds given a liberal dose of the HF sketch *without* toon lines (as in image 2 here) with the actors using a combination of the standard blender toon renderer and the freestyle method depending on if it's a closeup shot or not.
Time to go pester the Blender devs to integrate Freestyle into the main Blender distro for an upcoming release ;)