Whatever happens in the future, thanks for all your (free) time and effort. I've been using SS from its beginning and sometime before that I was on MSS. It will be disappointing if SS dies a slow death.
My main use is to register a few DIDs in the US, which I can then time filter using SS. Additionally I have a couple of local backup voip accounts (via SS failover) that require registration to facilitate outgoing calls. Restriction to one sip registration would certainly make SS almost unuseable for myself, although workarounds (eg still in box C470ip) are possible. Currently SS provides all the functionality that I require.
If you're to introduce a charge for 'premium' functionality I'd like to suggest a multi tier approach, based upon the functionality's potential server load, with one-off charging, or perhaps a charge for a five year period. I'd support a one off fee of $35 if need be, although I would find it hard to justify on an annual basis.
A major issue seems to be server load, hence possibily implement a (post) charge (or even cut off) each time an account goes over a predetermined mips per month. This would also limit abuse and could be waived for certain individuals whom contribute to dial plan development.
The potential for abuse is significant and needs to be eliminated. Recently Pennytel temporarily blocked Voxalot registrations due to abuse with calling cards. A 'free for all' with SS could possibly result in future blocking of SS.
I'd like the free account to be only limited to six sip registrations, not one. Reasons stated previously. That, in addition to dial plans, is the major benefit of SS. One dialling instance is fine for my use pattern, unless I wanted to set up a calling card business