I've worn a kilt to the office many times and my basic rule of thumb is that I wear what I would wear if I had on trousers instead. My current boss has no real objections as long I have do not have any meetings scheduled outside the building (I sometimes have to meet with high-level government officials). I have found that a kilt jacket, if wearing a tie, helps the overall effect.

My general experience has been one of acceptance, particularly by female co-workers.