Yup, you can count me in!
J is 8, dx with Asperger's last July, thrives on the classroom structure but falls apart on the yard/lunchtimes and frequently (until fairly recently) has a meltdown after school from the tension of holding it all in. Several professionals have told us that this is the norm for Asperger children - they attempt to conform during the school day and release their tension when they get home to a safe environment, where they can do so without being judged or punished. I know for sure that J is motivated by fear of humiliation, and holds himself together even harder because he doesn't want to break down in front of his peers. I can always tell when he's been picked on at school because his anger will be that much greater when I pick him up at 3.20.
I've been doing a lot of anger management work with J recently and he's now learning how to release this stress in more appropriate ways. Nowadays he'll come home relatively peacefully, read the Beano for ten minutes then spend another twenty bouncing on the bed playing The Killers at top volume (same track on repeat, natch). After that he's settled and ready for 'life' again, but without that outlet he's barmy and his irritability will continue till bedtime.
Having said that, just last Friday he came home from school, 'bubbling' with a rage just below the surface and I didn't know why. Within a couple of hours he had escalated into full blown, hour-long meltdown and ended up ripping a banister spindle off the staircase, later telling me that he'd intended (in his rage) to use it against me as a sword. Once he'd calmed down he was able to talk to me quite easily about his intentions but he also knew how far out of control he'd been at the time. This is a fairly recent development - he now knows he's safe to talk to me about this because I won't judge - we talk about his anger in a matter-of-fact fashion so that we can come to terms with it and begin addressing it. Incidentally, the rage on this occasion came not from one particular incident but from a general feeling of unease and unsettledness that J couldn't put his finger on, it frightened him and that was what set him off.
The people who tend to blame the standard of parenting do so, IMO, from lack of awareness and understanding and how stressful it can be for our children to live like this each day, being bombarded by sensory and environmental stimuli which typical children don't even notice, never mind cope with. These things can be extremely unsettling for our children and those professionals who can't think outside the 'normal' box have a hard time grasping the extent of the problems. There's a tendency to think of autism (and especially Asperger's) as 'normal with a bit extra', when it really needs to be looked at with a completely different perspective to understand it fully.
Another thought for your 'specialist' - photocopy the relevant pages on anger/meltdowns from Tony Attwood or something similar - there's a great book called Asperger Syndrome and Difficult Moments - Practical Solutions for Tantrums, Rage and Meltdowns (Brenda Smith Mules and Jack Southwick) - and hand it over at your appointment as evidence that meltdowns are part and parcel of Asperger's in most cases.
Good luck.