Same advice as with the rest of .be extensions - hold on to them and wait for the .be market to become crowded. If it doesn't take off in a year, let the name drop; if it does, however, you'll be looking at substantial demand for your name.
Don't bother selling .be's now, though - unless you got something like poker.be or casino.be, these TLDs are totally worthless, if only because they're still free to register.
So cross your fingers and wait a year - the free registration period should end on Jan 31, 2006.