Asterisk@Home is a useful system for a wide range of purposes. The costs are minimal - thanks to it being open source - it is able to work on older computers, and setup is fairly easy. The main negative is that some of the documentation in the manual and in the Wiki for advanced features is a bit lacking, so you may have to struggle a bit if you need to use them.
AAH provides a variety of useful features that enhance its business use. You can make a queue for putting calls on hold and also forward calls - just like a standard PBX system. System users also have web access to voicemail, which includes the ability to change preferences, manage and listen to messages. AAH can even e-mail voicemail messages to you if you like, and if you aren't at a computer, you can also access the voicemail system from a phone. There is also a "digital receptionist" that lets you direct callers using prerecorded messages.
AAH's simplistic setup makes it ideal for small or medium-sized businesses that just need something that works - with few questions asked. If you need a more sophisticated system, the standard version of Asterisk will be a better fit and can be optimized by a professional. Asterisk@Home shows that you no longer need a costly, complicated, vendor-managed product to have a full-featured and flexible PBX for home or small business use.