Pros: Voice quality, features, account management via website, and price
Cons: Customer service
Summary: Switched to VOiP.com after the Sunrocket meltdown. It took a while to transfer my number, but once it was released VOiP.com had us going right away. Voice quality has been good overall, and I can even use my line to fax. Quality ups and downs have been almost entirely directly attributable to my cable internet provider (Roadrunner via Time Warner) who has had numerous jitter, delay and QOS issues along with many disrupted service incidents.
VOiP.com's phone adapter is excellent quality equipment and came with very clear and precise directions as to its installation. Everything was color coded on the gear, and the diagrams matched up exactly; well thought out. The shipment arrived right when they said it would.
VOiP.com's account features are excellent and can be managed easily via their web site which is well designed. Voicemail options can also be accessed through the voicemail interactive menu after calling into the system for messages. Their voicemail system can also cause your phone's Message Waiting light to blink if your phone has that feature, a fact that they don't publicize for some reason.
The only real disappointment about VOiP.com is that their technical support is difficult to access. They provide some extensive FAQ's, but going beyond that level and getting to a human is difficult. Fortunately, once my equipment was installed there wasn't much to ask about except when my old number was going to be transferred.
Overall I'd recommend their service. The price is right and the quality is good. Just be ready to grind it out if you need technical support.