Why is everyone complaining about Apps accounts not being able to sign up? It says right on the "features" page http://www.google.com/apps/intl/en/business/features.html "99.9% uptime SLA" which means that if they add a service with less than 99.9% uptime, they're going to lose money. They haven't even finished writing Google+ for normal users, there's no way they can make promises about support yet.
Others have pointed out that the SLA isn't an issue. As for the separate service thing, there was a recent transition that was supposed to rectify this, merging the Apps and regular accounts services. The page you link to is about the need to remedy clashes caused by this transition.
During this process, users who maintained secondary accounts were encouraged to merge them into their Apps account. I used to have two accounts, one for Apps services on my own domain, and another for things like Reader. I now only have one, my Apps account, because the accounts clashed and had to be merged.
So the doubly galling thing about this Google+ farrago is that a) it proves that the accounts transition did not in fact stop Apps accounts being second-class citizens, but also b) most of us no longer have our secondary accounts, because we merged them at Google's insistence.
Add to this several years of teeth-grinding annoyance at the incompatibilities between Google Apps and the rest of the Google world, and, well, that's why people are complaining. :-)
But then I have to imagine that the tentacles of all these services intertwine in such a way that introducing G+ to Apps may not only cause G+ to fail but also supported Apps services.
I don't think that's the reason. 99.9% uptime is plenty. Uptime in SLA is defined as "Monthly Uptime Percentage", which is explained as follows (http://www.google.com/apps/intl/en/terms/sla.html):
"Monthly Uptime Percentage" means total number of minutes in a calendar month minus the number of minutes of Downtime suffered in a calendar month, divided by the total number of minutes in a calendar month.
For average month of length 30.4 days (~43776 minutes in total) that means acceptable downtime of 437.something minutes or 7 hours of combined unavailability.
Minding all of that, there is also a term "Google Apps Covered Services", which is explained as:
"Google Apps Covered Services" means the Gmail, Google Calendar, Google Talk, Google Docs, Google Groups and Google Sites components of the Service. This does not include the Gmail Labs functionality, Google Apps - Postini Services, Gmail Voice or Video Chat components of the Service.
So, legally speaking, there is no uptime guarantee for Google+.
During this process, users who maintained secondary accounts were encouraged to merge them into their Apps account. I used to have two accounts, one for Apps services on my own domain, and another for things like Reader. I now only have one, my Apps account, because the accounts clashed and had to be merged.
So the doubly galling thing about this Google+ farrago is that a) it proves that the accounts transition did not in fact stop Apps accounts being second-class citizens, but also b) most of us no longer have our secondary accounts, because we merged them at Google's insistence.
Add to this several years of teeth-grinding annoyance at the incompatibilities between Google Apps and the rest of the Google world, and, well, that's why people are complaining. :-)