I had the same issue on my MacBook Pro unibody early 2011.
After installing mountain lion I noticed that my battery was draining faster and suddenly the panel started to warn me to bring the Mac to service batteries.
I went to the apple store and they told me to buy a new battery: it was 14 month old, with only 79 recharge cycles!
It had only 29% health (current capacity [mAh] / design capacity [mAh]).
Now I have a new battery and in 2 recharcge cycles already lost 5% of its health!!!
The new battery was OK since I put the Mac in sleep mode for some hours.
I noticed that the Mac drains down a lot of battery during sleep, but this is not the last bad news: when it wakes up the health of the battery is decreased!
Anybody else is experiencing this? How many of you had to buy a new battery because it was under 3.000 mAh (macbook pro unibody early 2011) against a nominal capacity of 6.900 mAh?