What does the company do well? Asterisk allows to set-up a VoIP/TDM infrastructure quite easily at a reasonable price. Asterisk can also be set-up on a cloud server to get a centralised VoIP network.
Moreover Asterisk is open to add-on and customisation for software editors that need to integrate telecom functionalities to their solution.
What does the company not do well? As Asterisk is a software, it is not doing codec transcoding with dedicated hardware, so voice quality is reduced when you have peers with different codec possibilities.
What about the company do you wish you had known before purchasing? Asterisk is a free software that anyone can installs on a Linux system.
However you need to know that if you need TDM interfaces, you need a dedicated hardware card (which cannot be free of course). If you need need codec transcoding (g729 for instance), you need dedicated licences.
And if you want a easy-to-use management interfaces, there are various free and paid solutions, but I would go for a paid solution with service included.