I have just upgraded Exchange Server 2010 x64 to Service Pack 1 on W28 R2 x64 Stan. No issues concerning the (static) licence key. Only had to install about 5 hotfixes before the upgrade could start. So confirmed the usefull information from Myhken
after several days of playing on SP1 can confirm as above that everything is ok, even forefront for exchange is working with updated edge service! goodluck 2 all!