I’ve had Acorn in my list of applications to review for months, and I’ve only just got round to it. I wish I’d got there earlier. Acorn is quick and powerful, and that’s because it employs your GPU to do soe of the processing, and it includes a number of filters (based on OS X’s CoreImage interface), all of which is wrapped up into a nice little application. If you can’t find what you want, there are ObjectiveC and Pythong plugin interfaces, but I haven’t investigated it yet. Of the alternatives, the most talked about is Pixelmator, closely followed by Iris. Pixelmator is a closer approximation to the way that Photoshop operates, and in some respects I prefer the functionality and the feel of Pixelmator if I was looking for a Photoshop replacement, but there are other elements I don’t appreciate. The flashy graphics and animations when you do different operations seem superfluous to me.There are nice touches in both applications – the stamp tool in Pixelmator is particularly good (although I prefer Photoshop), while in Acorn the crop and select tools provide much better feedback during the select operation than even Photoshop.Iris is less polished, but shows some promise. There are some annoying oddities (I used 1.0b2, 367), like the image opening at pixel resolution, rather than being scaled to screen size, and the lack of specialized cursors can make identifying what you are doing and the potential effects of that process difficult, but the image editing and manipulation is very quick (particularly on stamp and touch up operations). It is, however, a bit memory hungry at the moment. Any of these solutions would make a good alternative Photoshop and Photoshop Elements if you don’t want to go down the Adobe route.Of these I currently prefer Acorn – it’s small and lightweight and the interface feels much more polished and easy to use. Certainly I’d consider it as an alternative to the larger packages on a laptop if you wanted something while you were traveling. I can’t get by without Photoshop because of the image scanning and editing I do, but occasionally I want something more extensive than Preview when I’m on the move. Of course, this could change – all of these tools are being actively developed and so it’s likely that there will be some leapfrogging along the way.