I joined that same french server aswell xD But hey, it was the only one not labelled as "full" but as "heavy"
OT:
The first day was very stable for me, i logged in at around 9 PM Berlin/Denmark time (8 PM UK time) and i had next to no issues at all, the only real problem i had was at the start of Korriban i had horrible fps, logged onto my smuggler (on that french server :P) and played with no fps-drops at all, later i logged back to my warrior and had loads of fun with high fps
Overall i think the first day was a really smooth and successful day.