Escrow can be a good indication that an ICO has a good and pure intentions or basically not a scam ICO. I've been into a project that's using an escrow for now and it went good so far considering that the campaign manager is very trustworthy too.
Escrow adding our trust on the ICOs. Could be a guarantee, i think it could be yes and no. With escrow, there is good will from developers team and i think we could trust if escrow from reputable company or person