Look down the side of the vehicle to notice any warping. This could be the sign of some kind of frame damage. Also feel along where the repair was done in order to see if there are any "edges" that could be around where they used a body filler that could eventually fall off, or cause other cracking problems. Make sure the door operates well with no sticking or noises.

As always, take it to another mechanic and ask them to look at it. Have them put it up on the lift and examine the repair.