Before you start reading, I will first say that this review is an overall review to the whole series, not only Season 1 in particular.
Now onto the actual review:
It was a fun watch. It was interesting and funny enough to keep me going, but it's missing something special for me to say that it was magnificent. I have to say though that Season 2 'Zero no Tsukaima: Futaki no Kishi' was the best. It kept everything to a good balance and the ending was amazing. Only to be spoiled by its sequels. Season 4 'Zero no Tsukaima F' was a close second. It tried to replicate all that was good of Season 2, but you can't expect the audience to fall for the same thing again. BUT what Season 4 had was a good and solid conclusion to the series.
TL;DR - Wouldn't recommend it, but a good watch nonetheless. Stopping after Season 2 would make the experience better.