I have used Tile38 for a couple of internal demo experiments this year and hoping to push the projects into production next year (budget allowing).

If you are looking for a realtime-GIS with geofencing support out of the box - it is an ideal match.

Docs really are great. Its very easy to get quick demos up and use. The code base is a joy to work with. It is a really really good project.

Would also love to see a write up of the 11 million points with Tile 38 - that is a really nice demo.