I've been running Cisco CallManager and Unity in our house for a couple of years now. Actually it started out as CallManager Express and an answering machine and went from there. I've looked at Asterisk from time to time and even had it running next to CME for a little while. I used it as a SIP gateway to Broadvoice. Aside from Broadvoice being pretty bad it worked well.
I'm coming back to Asterisk now. See, one of the problems with me running Unity is a 30 second limit on messages with the demo license. There are other difficulties with CallManager that make it less than desirable for home use. With Asterisk I'll have unlimited voicemail and I'll be able to do other cool things like Find Me/Follow Me to a softphone on my laptop, streaming MOH, telemarketer filtering...etc...
So far I have *@home installed under a virtual machine on Virtual Server. It didn't like 256mb of ram much so I bumped it up to 512mb. Hope that's enough for now.