Tom Keating of TMC writes up the Jazinga box. Unlike Tom, I've been using my box up until the latest round of home remodeling, and can only give it the highest form of compliments. It's VoIPWatch approved.
Now for the sake of transparency, we've been helping the leadership of Jazinga get their box out and tested. While there were some typical alpha challenges nothing was insurmountable.
Here's why I like it.
1) It works with SIP
2) I can use PSTN or IP Phones with it
3) You don't need an IT guy to set it up or manage it
4) Jazinga provides SIP credentials so I can use a softphone from anywhere
5) It's also a router and wireless access point..that means less boxes in the rack
If you need a full featured IP-PBX for your home office or small office, Jazinga is a very good bet and well worth its price.