We have been using this product for about 4 years now with several different clients across various industries such as financial services, retail industry etc..
I can honestly say we are very happy so far! Nothing really comes up during my day nor do i hear any feedback or complaints from users. Sometimes they get stuck but usually just restart their computer and its ok again. Highly recommended if you're looking into getting unified communication solution through an SaaS provider!! If there were anything that could be improved upon then maybe more customization options would help? It's great being able to logon remotely via mobile phone / tablet when I am out of office without having multiple devices.