What does the company do well? Asterisk does a great job of providing standard PBX features for an office environment. It can even be used to connect geographically disparate locations in to one cohesive phone system.
What does the company not do well? It is not really meant for ordinary people to configure and maintain. You need a great deal of knowledge about how asterisk works, how to maintain an operating system (linux usually), and how to connect your asterisk system to SIP or PSTN circuits to enable calling.
What about the company do you wish you had known before purchasing? There is no price to purchase Asterisk. It is free, open-source software.