Claudia,
I still use the old UpDox... but that's only possible because I haven't yet upgraded to AC 4 yet... just procrastinating while getting other things cleared up.
I also had concerns about the new pricing model... I was in email contact with Andy Barbash (their co-founder) about that and he led me to believe that the ultimate cost is essentially unchanged, in his words: "apractis clients of ours (that is the magic $90 a year you pay us for a support membership) get a special discount to UpDox Network that nets only $25 a month instead of 50 and the AC $20 a month goes away". The 'AC $20 a month' being the monthly interface fee.
Again, I haven't used the new system, so I'm not sure I'm going to keep it. The good thing about UpDox was the integration with AC, making IMPORTING faxes very easy... rather than saving the PDF fax to a drive then importing, it would import directly from UpDox. There are a few other features I liked including sending emails with some security features, but if I end up getting rid of UpDox, I'll likely just use Mozilla's Thunderbird or Outlook or something like them.
You don't need to have UpDox to use Onebox, so you can set your email client to retrieve the faxes/emails/etc from Onebox just like UpDox does. But, if it's true that you only use Onebox to receive faxes digitally, you'd save money using something like pFax, where I think it only costs $4 a month for unlimited pages of faxes received. I use Onebox for several other features that you can't do with pFax. I'll have to look into the SnappyFax though. But in the end, your concerns about staying paperless definitely doesn't depend on your use of UpDox.
Good luck and keep us posted on your progress/decisions,
chris