Yeah, every betta is different when it comes to temperament, and how it acts in a store cup may not reflect its true personality when it gets into a tank. For example, when I first picked up Romeo, he was extremely active in the cup, flaring at the other bettas and swimming around. In the community tank, he's very peaceful with the cories, although I have seen him flare and chase on occasion. It's usually pretty short-lived as cories are far too fast and have a lot of places to hide.
My other two halfmoons could NEVER go in a community tank. They were docile in their cups, but in the divided tank, my word, they're active all the time and pretty darn aggressive.
Just be sure you have a backup plan in case the betta doesn't work out in the community tank. :) Good luck!