For VoIP that has already entered a voice call, there is still much room for improvement through VoIP fax.
Have you tried faxing on a residential VoIP line? I have, and the progress is not going well. After doing some research on this topic, I found that voice traffic and fax traffic are best run through two different codecs. That's why when most VoIP carriers sell commercial accounts to you, they include a free add-on fax line and fax-specific codec for faxing.
You can fax on a voice VoIP line, but this is not recommended. You can fax a page or two via a voice VoIP line, but it may take several attempts to complete. The reason is that when a fax tone is digitized into a packet, the packet is lost. It's not important to lose the packet on the voice, because even if you lose a bit of the packet, you can still hear and understand what the person said. However, when there is a packet loss on the fax, any point may actually mess up the fax. The result could be a fax error, and the error message is even dropped. When faxing via fax codec, packet loss is minimized and faxes usually reach their destination, but for large faxes [more than 10 pages], the chances of fax success are reduced. It is recommended that you plan to fax a large number of customers to use as a fax machine for the scanner and convert the potential fax into a .PDF file so that if the fax is invalid, the customer can send the fax by email.
Programmers have been thinking of better codecs, so it is only a matter of time before VoIP providers come up with more reliable fax codecs. VoIP will continue to exist, and VoIP providers are trying to overcome all objections from small businesses to get business, and faxing is a big issue for small businesses. I am confident in VoIP providers and come up with a solution that works at the end of 2005.
Faxing is just one of the things to consider before choosing a VoIP solution. In fact, there are many things to consider when choosing a VoIP provider. Educated consumers usually produce satisfied consumers. You can compare VoIP providers side by side at http://www.voipchoices.com/