Doesn't neccesarily mean it wasn't real
Remember when he flung the Enterprise into a confrontation with the Borg. That wasn't one of his illusions or creations.
I've often wondered if the events of Tapestry were an illusion. I suppose Picard could look up the history of the events and see if he altered history, or if history played out how he remember it. I do like how Picard is grateful to Q for the experience, and I'd like to think Q was trying to teach Picard something, rather then just torture him.
To go off on a tangent, which is unusual for this board I know :-
When Q threw the Enterpise into its first confrontation with the Borg, did he do them a favour, and was it worth the 18 (?) dead crew members.
I also thought that their confrontation was what alerted the Borg to the Federation, which in turn sparked their first invasion. This was down to Guinan warning Picard that now that the Borg knew of their existance they'd be coming. However, its revealed that the Borg had already destroyed a Federation Colony, and would already be aware of them. Guinan could have been referring to that incident. Also, why didn't Guinan warn the Federation about the Borg earlier?