Everybody is kinda saying the same thing but here is the actual history. Version 1 is obviously the first version an while it worked well with some nodes, it had issues with others where Ray's controller had no issues. The distance between the controller and the first node was fairly short. If you have a version 1 and it works with the nodes that you have connected to it, I would leave it alone and go with it.
Ver 2 was a redesigned SSC that was designed to correct the problem with the Ver 1 controller but the problem actually got worse. This controller has issues with flickering as well as the issues that the Ver 1 controller would sometimes have. If you have a ver 2 controller, I would consider performing the mods to turn it into a Ver 3 controller.
Ver 3 is really just a modified Ver 1 or Ver 2 controller. With this mod, the issue that caused the problems with good nodes not working, flickering, and the required short distance between the controller and the first node are corrected. The instructions and firmware for this mod can be found in the WIKI and when completed, you have a rock solid dependable controller.
Ver 4 is the newest SSC. It has been once again redesigned by RJ to make it smaller, less expensive, and rock solid. With the controller being smaller and the ability to have a longer lead length between the SSC and the first node, it is much easier to hide the controller and it works pretty much flawlessly.