I have been using PBX for about 8 years now, so far it has never let me down! Great call clarity even at great distances from each other across different offices/branches! The price is also very affordable compared to others out there (like Vonage).
Nothing really that stands out as an issue or dislike - everything works well enough! We are still looking into some features of this product but nothing too major yet. If you want super cheap calls between branches then go ahead-it's worth every penny!! It allows us all over our office buildings to communicate freely without having issues like dropped connections etc which was happening before we started working here.