I've had mine since early January. It did seem to take the battery meter a few days or so until it seemed that it was definitely getting better life than stock. I just did a full 8 hour charge the minute that I installed the battery, used it until the phone would no longer run, fully charged it again, and have used it just normally since then - meaning that I take it off charge when I wake up in the morning, sometimes charge it while I am showering (I work out right after I get up in the morning), and then plug it back in when I go to bed.
The best remaining charge when I had stock (as I remember it) was 40%, and it was usually around 20% at the end of the day. Now it's unusual for it to be below 50% on the days when I do not charge while showering.
Li-ion batteries may not need calibrating, but the device that is monitoring the charge state and calculating the remaining life may (and seems to.)
As for the larger battery, I briefly considered it, but one of the reasons that I chose the Eris over the Droid was its slimness and easy pocketability. If I wanted something thicker, I would have just gone with the Droid. But, that's just me ...