It does look small, but the people I know who have had one both said they were very filling. Though, they are dainty little people, I'm sceptical that I would be filled up.
I like to make a homemade one, but use a pre-made salad mix with it.
Beelzebab - one of the stalls at the Street Diner in brighton - has a vegetarian doner kebab that is supposed to be amazing. I haven't had a chance to try it yet...