I assume, the missing features are more of programming issue....One thing PBXes have done, is leave most of the usual Asterisk PBX interface untouched, which proves confusing until you get used to it.
Some other issues at PBXes are:
-The monthly price for premium
-They are picky about having multiple accounts. If your account becomes blocked/limited either going paid or making $50 donation is the only way to regain access to it. Getting in touch with them seems hard (there isn't much contact info)
-Their Premium-Only forums mean new users test driving the system on their Free Plan get no initial support
That said, VoXalot (Free or Premium) is ideal for VSP/Dial Plan configuration. It can then be used in conjuction with PBXes or MySipSwitch to make up for certain features...
I am in the process of testing something that should also make it possible to use your VoXalot dial plans in conjuction with ANI CallBack (...suspense grows
)
Finally, this
Voice-over-IP gateway for Google Talk, MSN and Yahoo Users caught my attention after mgoebel's post... It has been on Gtalk2Voip's site for a while and I haven't heard much about it. One thing that seems promising (which I need to test) is that the software runs on just about any JAVA capable phone. On the other hand GTalk2Voip will let you specify VoXalot as an outgoing provider (and may even let you receive--iffy about this-- your VoXalot calls via that software on non-Symbian phones that do not support VoIP registration or Fring otherwise)