I agree its casual, as its not really meant to be a bag at all. it's an accessory to a bag. However, I see many people carrying it as an everyday bag or wristlet.
Maybe cause that's all they can afford or just their personal prefetence. I don't mean to sound like a snob about it. I think as long as you're happy with it, that's all that matters.
But since you asked and you are looking for advice, I would not carry it as an evening bag. I would probably look into less expensive choices (other brands) and put your money towards what really works for your lifestyle.
I kind of equate it to people that buy the base line Mercedes without any extras because that's all they could afford. they like driving a Mercedes. For the same money, one could get a top of line something else with tons of features. it all depends on how you want to spend your money.
but i wouldn't carry the pa as an evening bag. I think it would detract from your look.