Toktumi.com is another service. I had much better luck with them than Grasshopper, FWIW. We eventually moved on to our own platform (based on Asterisk initially, then FreeSwitch) for more flexibility and control. RingCentral should be avoided.
[We also frequently hire FreeSwitch and Asterisk consultants, if anyone on HN wants to be added to our vendor list.]
Sure. Several features didn't work as advertised, or only worked intermittently. They always fixed the issues eventually (and apologized), but we were losing customer calls and faxes in the meantime. Sometimes the service didn't work at all...outages and transfer issues led me to their customer service, which sucked. It was infuriating to be paying for advertisements that featured the 800#, only to have the incoming calls/faxes be lost or misdirected. When you have offers for a home lost in the ether, you want decent customer service. Unfortunately, their entire customer service staff seemed to be on their forum - monitoring and rapidly deleting any complaints or negative comments. At one point, they banned one of my employees from their forum because she was trying to resolve an issue. It drew too much attention to the problem.
I believe they've taken in additional funding since I used them (?), so they may have improved. I've not had problems with any of the (dozens of) other 800# or virtual PBX providers I've ever used though, so I was left with a fairly bad opinion of RingCentral.
[We also frequently hire FreeSwitch and Asterisk consultants, if anyone on HN wants to be added to our vendor list.]