P: Blur/Sharpen Adjustment Layers

Convert the layer to a smart object.
Then apply blur to it. Now you can adjust / remove the applied blur @ what ever point of time unless you merge the layer.

It still could not allow live updating of the filter effects, and would still require either turning off filters while you worked below them, or an explicit update step and recalculation of the filters -- basically the same as what you have today.

Also, it would bloat your files, use more memory, and cause more than a few problems because you're using a heavyweight abstraction for what could be each and every layer.

No, that's not going to work.

I have a new idea how this could work out... (I'm not a programmer, so I might be wrong about this):

What if behind the GUI surface, Photoshop would be creating a smart object from all the layers below the new adjustment layer, but we can still see the separate layers of the smart object within the same project underneath the adjustment layer. So technically it would still be the same as it is today, but from a user perspective it would seem to work the same way as in AE. I think that would be a useful improvement to the workflow and yet you would get rid of the problems that come with "real" adjustment layers for filters.

@Chris: I know. To me, there's nothing wrong with that. Works fine for me in AE, why wouldn't it in PS?

And only some After Effects "effects" are live like adjustment layers - most turn off the effect when you work below the effect.

Remember, After Effects is dealing with images that are generally much smaller. HD video is 1920×1080px in dimension - an image size that readily fits on native monitors, thus fits in the GPU's memory space. Photoshop documents can be much, much larger 300,000 by 300,000 pixels. It's non-trivial to make the same effects apply to images that an order of magnitude larger.

Ah, someone has made this suggestion before.

Well, I see you're saying that it's not possible because performance would break down if filters were to be applied as adjustment layers.

But then again think of how well After Effects can handle the very same task. Even with more than one effect on each adjustment layer. I did read the article from the first comment, but please remember CS1 was released almost 9 years ago... I think the cicrcumstances are different nowadays!

I know that you people at Adobe can do it! Smart Objects are good. But in many cases not really what I want. Projects can get uncomfortably complex. I'd really love to see this happening. And I think there are many out there who think the same way.

I've been working a lot in After Effects recently and have become very comfortable with using Adjustement Layers to add effects. I enjoy using Adjustment Layers in Photoshop, too, but yet they're not the same as in AE.

Now what would be really cool to see in a future version of Photoshop:
The ability to apply Smart Filters (e.g. blur) as Adjustment Layers kind of like in AE!

This would be way more handy than having to handle multiple Smart Objects.

We have that - it's called "save" on a smart object.

Even low quality would be prohibitive for a live preview using adjustment style filter layers.

That makes total sense to me. Perhaps the solution is a "render" button. So when you change something it gets reset to low fidelity until you hit render. Similar to how you handle 3D objects.