I've updated from FF to H7 and everything seems OK, I'm surprised how fast the update went
It now seems to run a bit faster, I hope the battery life will be longer
Later edit:
the battery problem seems to be solved!!! in 4h 30' I only lost 3% of the battery with EDGE connection,
auto sync disabled, and had a 5 minutes call, 2 received texts, 1 sent and played Labyrinth Lite for around 10 minutes.