Rate my Rasberry Pi UPS
A linear voltage regulator converts excess power to heat. 

So dropping 7V to get 5V is worse than 50% efficiency. 

At 0.7A and 7V drop, that would be almost 5W of heat. 

So you'll need a decent size heat sink. 

Look at DC-DC converters instead if you care about that energy waste.

Edit: to incorporate ACD's comment:
"lead-acid batteries are usually around 14.5V when fully charged. At 1.2A that's 11.4W"