When my subscription ends with Shojo Beat, I don't know if I will renew it or not. I subscripted because of Nana. I like Vampire Knight too, so I might keep up my subscription. I guess it depends on how the format is. I haven't care much for the new format changes they have been making lately.
I know that they are up to issue 6 in the manga book releases. I have 1 - 4. The local anime company went out of business when 5 came out, so my order got canceled and I haven't been able to find anybody with a copy of it. I notice that 6 has plastic over it. So I'm guessing the maturity level went up in that issue.
I do applaud Shojo Beat for their choice is no longer serializing Nana because lowering the mature context would probably take away from the storyline. So I think it is better they went straight to book release now.
Through
Rightstuf you can preorder up to issue 10 and they don't charge you until the preorder ships. They have pretty good prices.