How safe is the metro at 5:30 in the morning?

I'd say it would be the safest time of all. The drunks are sleeping it off and the pick pockets are waiting for it to get crowded enough to operate. Nothing but people who have to get to work early.

I agree with Sam. Note that Chatelet station is huge and multi-level.

Perfectly fine. There are not many people around at this hour - most people start rushing to work or school around 7 AM.

It's fine, as everyone else has said.

Not at 0530 but I've often been at Gare de l'Est one hour later ...fine. Some tourists are already at 0630 waiting to catch their trains.

Thanks everyone for all of your responses.