jizzer, I don't personally know how many spots typically open up or how many people typically come off the list. Reliable numbers for GW are hard to come by. I have heard that there is usually good movement off the list and it is therefore a decent list to be on.
But, it does seem as though GW hasn't started making calls yet. They have sent some acceptance letters to alternates (naya and KDocGirl), but at least one of these was dated back in April. I don't think that any post May 15th spots are being filled yet, at least not to a significant extent. In the next few days, I think the "they called me" posts will start to trickle in. Until then, don't sweat it too much.