I think a problem for a photoshop replacement is the brand of photoshop. If you want to cooperate with advertiser agencies, you HAVE to use photoshop. If you use another software, you should hide it. This is not a good situation, but a lot of advertiser agencies hired people with low knowledge but big show-off. This people you never can persuade that an alternative software is not a sign for your disqualification... Only chance here is that another software can built up also such a good reputation.