Keep in mind the system is only as good as its usability. Make sure that the user interface is not so complicated that the people who will need to use it give up in frustration at the too numerous options, badly organized options, or uber technology.
If children are going to be using it for video or an elderly person for controlling the overhead fan, these factors need to be taken into consideration. Also, if in the future the home is up for sale, an overly complicated system could break a sale, while a home automation system that really delivers can bring potential buyers to the dotted line.
You may want your system internet accessible. How nice to be able to crank up the heat in your house as you edge out of the airport parking lot toward home via your laptop or PDA. Some systems allow you to log on to a secure website, see what's what back home. Then with a mouse movement here and there you change any of the settings to your satisfaction and needs.
Your home PC system may need upgrading and a phone modem may be woefully inadequate for handling this level communication. Upgrade to a broadband connection before you go with these remote possibilities.