The idea of a robotic lawn mower is appealing, but it seems that most of the robotic lawn mowers currently on sale are overpromising their delivery somewhat. Amazon reviews are in many cases a mixed bag, and it seems the effectiveness and use of such a device can only be correctly gauged when actually letting it loose on the lawn you intend to buy it for.
Nevertheless; what would be the main parameters to look for in a robotic lawn mower, and what are the major painpoints that still exist?