I'm thinking I must also talk about the opponents of Cyberboard. There is many game engines that compete to get the #1 position in gamer preferences (right now, undoubt, it is holded by Cyberboard). I will talk my little experience with them, but I guess it is time to talk about the most powerfull opponent that Cyberboard has faced until now: VASSAL
At the beggining, VASSAL was VASL (Virtual Advanced Squad Leader), a very popular java application to play ASL by email and real time. Rodney Kinney had many request to develop the application to support more games, and VASSAL born. Finally, VASL get obsoleted and was abandoned to reborn as VASSAL module. This is, like a classical story of greek mythology where Jupiter eat his sons, the history summary of this tool.
VASSAL is developed under Java, so you can run in every platform. Although it was initially very difficult to develop modules for this engine (requiring programming skills) it seems now it is not a problem seeing the increased modules available for players. It is also a more organized community than Cyberboard, providing all modules available in the same site than application download.
His weak points are, in my humble opinion, is more suitable to real play than pbem, and the java technology uses more computer resources. Big modules can gives you memory problems when using the tool. Also, the learning curve to begin using this tool is more stepped, but one you got it surely will be comfortable using it.
Nothin more can I say, except than I still prefer using Cyberboard by one major reason: my current schedule don't allow me to sit down with the computer to real time play and unattended pbem play fits with my family and work times. But surely it is not your point, right?