Hi I have used it on its own and mixed with 50% peat moss both have proven extremely good planting media. The plants below are growing in 50/50 mix, with about the equivalent of 1/10th EI ferts dosing.
It took about a week for this tank to cycle (heavily planted), however, I also added a minuscule amount of peat from my old filter to the soil substrate, no more than a few teaspoons full, which I think was perhaps enough to inoculate it and speed up the cycling and mineralisation processes.
I didn't do any water changes for the first week, and neither did I use established filter media. During that time ammonia, nitrites and nitrates peaked at a reasonably high level then quickly returned to a trace and remained stable.
As for using it uncapped, I should imagine it would settle eventually but it would be very easily disturbed, so depending on your urge to move stuff around turbidity could become a longterm issue.
I often use a soil retainer/gravel tidy (below) and then cap with a few cms of sand but you could equally cap with a Gucci substrate of your choice, such as columbo flora base which would look natural and have the obvious added benefits.
The links below have more info.