I use a Stargate as my primary hardware/computer interface. It works great with Homeseer and most other software programs out there support the Stargate platform as well. I am always looking at possible alternatives but so far I have never found anything that would be a viable replacement for my Stargate setup.
I'm using HomeSeer for the software. For the hardware interface to X10 stuff, I use a CM11A for the powerline interface and a W800RF32A to handle incoming RF (palmpads, motion sensors, security devices (DS10A)).
I wouldn't recommend that anyone start using a CM11A but I've never had any problems with mine (after years of use, it just sits there working fine).