A complaint I sometimes heard about the LiFePO4wered/USB (the only complaint really) was that the battery didn't fit well in the battery holder. This was definitely justified: being a perfectionist myself, it was something that bothered me as well.

There's a solution now: all new units will be shipped with a new battery holder and cell that provide a much better fit:

The new cell is smaller (shorter) because it has a flat top instead of a button top. The old battery holder had a reverse polarity protection feature in the plastic, and although the new cells seem to work in it, the feature is really designed for a button top cell. So I decided it was safer to switch to the new battery holder I've been using for the #LiFePO4wered/Pi and also use it for the LiFePO4wered/USB now.

The only relevant difference (aside of a much better looking unit :)) is that the battery holder pins are shorter than they used to be. I already altered the product brief to allow for the variation in physical dimensions a while back.