We chose to go with Cool Telecom when we were remodeling our office and had our land line ripped out. We liked this technology and the features it came with. We now have unlimited phone lines and have had as many as 15 simultaneous calls (we are a doctors office). Before with our landline, we only had 4, so it has definitely increased our communication with our patients.
We love the feature of the failover calls. When our internet service fails us, our phones roll over to our cell phones and patients are none the wiser with no loss in communication. We now get our faxes by email so any unwanted faxes don't waste paper and toner. I have an endless supply of email addresses for my growing staff so I no longer have to use an untrusted webmail (like yahoo).
The call quality is great and the speaker phone function on our Cisco phones is crystal clear. I can manage everything online from changing voicemail passwords to creating email accounts. I can use the monitoring feature and listen to a call to see what was REALLY said (which is handy).
It is set up to automatically start ringing when we open and stop when we close. All of the holidays for the rest of the year are set so I don't have to worry about "turning the phones over". I can even use the "cell phone bridge" to call a patient and it looks like it's from the office, when really it's from my car.
Couldn't be easier and I would highly recommend it.