Call quality is just as good as a normal phone line. Customer service is a disaster. It is very difficult to get hold of an actual human. If you call their number for support you are directed to send an email.
If one day you want to leave Teleblend then the process gets to be pain... to quote Teleblend "Please note, if you are porting your number to another carrier, your TeleBlend account must remain open until the port out completes at which time the account holder must contact TeleBlend (remember there is no human to talk to) to close the account per the TeleBlend Terms and Conditions. We do not accept third party cancellations nor are we notified of port-outs as they are handled by underlying carriers. Your TeleBlend account will remain open and continue to bill until we receive security information from the account holder"
Need I say more.
Keep away from this one.