I think open foregrounds are really cool. What is great about them is you don't have to worry about trimming a foreground plant and keeping that looking good. There are drawbacks to using them though, with a system using aquasoil the technique is to use small rocks between the soil and the sand creating a kind of barrier, often these rocks are dressed with moss. I found in my last setup the shrimp would always throw the aquasoil granules over the rocks and onto the sand, so it proved quite difficult to keep the sand clean. Also the moss grew very well on the rocks I used and therefore became a bit unruly and difficult to control. You end up with this thin strip of sand with an overpowering feeling of the plants coming in over the top, that is the mistake I made in my last layout, so if I were to use it again I would definately try to use more sand in a v formation so if anything the foreground was bigger.
In my new setup I'm not using sand I'm using e tennellus, this may well prove too problematic for me and I may well go back to using sand again as I do love the fresh and modern look to it. I did want to try growing a foreground again though as I fancied a change.