I don't think it will be hard to clean but there is more potential of mildew. Simple maintenance will take care of all your problems. I see more mildew problems with silicone and grout then I do on tile.

True it's only the grout lines you would have to worry about. I run a professional house cleaning service and have came across several types of tile where the client has used floor tile for a shower surround and the tile itself cleans up nicely, however the thicker the grout lines the more mildew it collects and we have go in with a tooth brush to clean it. Remember to check with the manufacture to make sure it's ok to use in the shower as well.