First formula feed - any problems?

[weeblueberry]

We're going to introduce a bottle of formula to my daughters diet after 6mo exclusive BFing. I'm just curious if, when anyone else has done this, their tummy has reacted badly and they've not taken to it well?

Asking mainly as im trying to decide whether to give her a whole bottle of formula or express some and do half an half. The problem with the latter is I've always found expressing hard so doing a half a bottle would take a good few sessions. Obviously I'd do it if it made a difference but if others have moved across with few problems I'd be inclined to give it a go...