I managed a decent size system pushing $40k/mo through VoicePulse. Most of it going to Uganda, Peru, and Fiji. The voice quality was never an issue except for VSAT or whatever.
My only complaint from years ago when I ditched them, through inheriting the new system is that they are constantly changing things that require user intervention. If you miss those emails, your phone system stops working.
If I wanted that I would hard code their IPs rather than using DNS.
Other than that, they had very good quality without any kind of direct link or real QoS.
Obviously, pushing that amount of traffic their way also got me same day replies from the CEO and if I really complained, and threatened to move the business, he jumped on a plane to come visit but I was gone to Iraq already.
Bandwidth.com is a bit pricey but great.
I try to negotiate out old paradigm terms that are not applicable to VoIP so much, such as channels. Sure, you can limit me to whatever number we agree upon, but I am not paying an MRC for them unless they are going to give me a layer 2 handoff.
Gafachi is good and pretty cheap too, I was bit surprised.