I've been using Photoshop for one thing or another for more than ten years. It's an indispensable tool. But the lack of any decent competition (yes, I know about Gimp and Paint.net, thank you) has left Adobe with no incentive to improve. They still add features, but in a haphazard way that leaves the menus not making any sense. The 16-bit processing is restricted in odd ways, so that they include a photo editor with a completely different interface before you even get into Photoshop. Once you're in Photoshop, you can't manipulate the hidden information that is too bright or too dark to be represented within eight bits.
But what really annoy me are the longstanding bugs. Some of these have been around since Photoshop 4.0 at least (We're now on 11.0, by the old count.) Here are three:
The cursor bug: Sometimes, the cursor tool will change from a circle showing the size of the brush to a cross-hair showing the center of the brush. The way to fix it is to go into File>Edit>Preferences, and change the Painting Cursors from "Normal Brush Tip" to "Precise Brush Tip." Yes, that's the opposite of what you want to accomplish.
The color matching bug: When using Image>Adjustments>Match Color, it's supposed to work like this: you select a region from one image, you select a region from another image, and the colors in the second image are bent to match the corresponding colors in the first image. It works perfectly, and gives beautiful results that would be hard to accomplish by tweaking the curves. The trouble is when you try to apply the remapping to the whole image, by checking "Ignore Selection When Applying Adjustment." When you do this, the colors within the selection change radically. It comes up with a new mapping, that is always worse than the mapping before the box was checked. I don't care what mapping you apply to the gamut of colors not included in my selection, Adobe: leave them alone, map them all to purple, whatever, I can cope. But the colors that are included in my selection, when I check that box, LEAVE THE MAPPING ALONE. IT WORKS FINE.
The Anisotropic Diffusion bug: Hidden away as a bullet on an otherwise useless filter (Filter>Stylize>Diffuse) is the anisotropic diffusion filter. This can be very useful for preventing jaggies when an image is enlarged, or for painterly effects. It basically smooths along edges, never across them. The trouble is, it is applied to a small region (368 pixel by 90 pixel strips) at a time. This leaves an edge which is treated differently between the two regions. It's done for speed and memory reasons. I think they've improved this one, but it's still present.
My hope is that Adobe will somehow come across this post and fix the bugs. I've also submitted them to their bug report website. But I'm not holding my breath.