The beta on the 17th is a closed beta for pre-orders only. Open beta (only for pre-orders I think even then) is sometime in late August, I think. The client took about a 6gb download for me when I got the NA beta one, and 7+gb for the Chinese one that I am playing on at the moment.
Ah well, guess I'll wait till they got trial periods and hope they are 14 days or so.