I leave my bags at the claim area all the time and claim them only in the morning. It's pretty safe. But again, the well known axiom of not putting anything really important in your check-in applies. Just bring your baggage claim stub and go to the unclaimed baggage area (just immediately right of the baggage claim area : you'll see a pile of bags just walk towards it .

Inside the transit area, there are free internet terminals. But they time out at 15 mins, which is annoying. If you have a laptop, bring an ethernet cable : you get free (no time out) internet on many of the sockets available. WIFI, on the other hand, will cost you and is spotty.