That's where we are too.
We're waiting to be sure that nothing that is currently working WELL with the non-MAPI release, breaks if we upgrade our production server to the public not(production ready) beta.
We already lost enough customers in the past because we break things when applying updates, having to rollback and are not capable of having a stable mail service.
In the meantime we pay for maintenance, submit bugs report (that are corrected, this is good) but never backported to the stable version we use.
So we have customers waiting since almost one year, that we fix some small but annoying bugs, but we must tell them to be patient and hold.. because we can't risk yet to use the mapi version which contains these bugfixes. (they don't care about mapi at all, just want bug fixed).
Some already resigned their contrat and went to another service provider.
To avoid more customers loss, we had to setup another mail service in parallel (took us 1 month), all based on opensource projects and that brings, let's say 80% of what SmarterMail as to offer, but also brings features SmarterMail doesn't...
We moved our most angry customers on it and all the issues they had are gone.
Don't get me wrong. I personnaly globally like SmarterMail for a lot of things and wish we didn't need to setup an alternative, but we had to act before losing complete important contracts only because the mail service has issues.
I hope the future will be brighter!