Testing the status of a battery

I just bought a Ford Expedition last month. We had an experience camping several weeks ago where the battery died and we had to get a jump start twice. We were camping so the car doors were open for a while, but now what I would consider too long to significantly drain the battery. The second time was the morning after the car was driven for about an hour. All indications are that the charging system is OK. Both the dash board instruments and the tests below show no problems with the charging system.

After a 7 hour drive, I used my little floating ball battery water checker and it showed that the battery is only just over 50%.

I took the car into both Autozone and Kragen. They both put their analyzers on the battery and tested both the battery condition and charging functions.
Both placed said that the battery and charging system was in good shape and that there wasn't any problem with the battery.

So my question is do the battery testing devices at the auto parts stores do a good job of determining the overall condition of the battery?

I know the floating ball checker is old school, but is it still reliable in determining battery conditions in todays batteries and can it be a better indicator of the battery long or short term condition than the electronic checkers that the stores use?