They're slow but steady for sure.
I now have a 20 L I'm setting up to be a low tech planted with more fast growing plants. I like the look of anubias a lot but yeah if I didn't have this other tank to fiddle with I'd probably get impatient.
On a side note, I picked up some purigen last night because the driftwood was still leeching tannins despite many hours of boiling and oh my goodness, that stuff works. It's clearer than it even was before I put the driftwood in.