I'm just trying to get a sense of the custom out there.

FYI - my T is an employee of the HMO -it's a traditional center-based HMO. He has never given me a reason why this rule exists, just that it is a rule. I'd have to guess that it's a first-come, first-serve situation, like FarmerGirl said. My T likely has more clients than he can fit into a single week - some of us can't be seen each week even if that's what we'd prefer, some of us will get an appt 5 or 7 days out, some will get one that is 10 days out.
I've gotten MUCH more comfortable with this method as time has passed. However, setting up the "regular" time for my son really triggered my own insecurity about not having the sense of commitment that I'd get from a regular time. Like Sunrise said "It made me feel like I mattered to him"....
With the HMO employee, there is no need for a referral and no limit on visits.

The logic that fails me with the HMO: If this policy is so strict, then why doesn't the on-line appt system enforce it? They spent 20mil+ on this highly secure system but FORGOT to have it include this rule? The system enforces multiple other rules that are specific to my membership (names of practitioners, types of appts I may schedule, do I have a referral, etc).
Velcro, like you, my co-pay has now become = to the lower medical co-pay under the new parity law.

My son's T is paid by the HMO, but is in private practice - none of the HMO-employed practitioners were available to see him. He's limited to 12 visits on the first referral.