I've been talking to some people recently and Krita came up in the discussion among bunch of artists and we all agreed Krita is a very nice program and many of us would be willing to switch to it as a main art software, BUT
The freaking eraser tool.. why? Why is changing the brush you currently are using into eraser mode the only option? Imagine doing a lineart and having to erase your lines with 5px brush, or having to increase brush size every time you want to erase anything twice, and having to look for the original brush size again? And i am aware you can switch to previously used brush, but that's nowhere near the solution since i usually use up to 5 brushes constantly.
It's not that hard to implement an eraser tool, just as photoshop has, or any other software, which would have it's own preferences and shortcut and would remain unchanged by the settings you change on your brush. So that we can switch between 5px brush and 200px eraser tool back and forth.
After doing some research, I can see this is fairly requested feature, one that i believe is deal breaker for whether to use Krita or not for others, as it is for me.
That's it, I'm a fan of your development team, i seriously think those folks at adobe need to be shown that by slacking off they get a run for their money. Keep it up guys and think about the eraser tool a bit please!

Hi Youghurt,

As stated on several other occasions this question was asked, we have discussed the eraser tool with artists, and the current method allows them to eraser with a similar texture as the drawn lines. It also works on the other tools, such as the rectangle tool, or even the gradient tool, as well as layers themselves. Artists who are used to it find the eraser mode very powerful.

Now, people have asked often if we cannot set an eraser preset to a hotkey. People have also asked us if any given preset could be set to a hotkey. That sounds kind of alike, right? But we were a little worried, how would we make the interface look good? Furthermore, what if people want more than any given amount of presets we give them. Therefore, the first thing we did when designing default python scripts for Krita 4, was make a brush switching script complete with interface. This was you can switch to any given brush, and if you know python you can customize it to take any number or presets or just write your own script that hardcodes favourite presets.

So, to set an eraser preset to a hotkey in Krita 4:

1. Tools -> Scripts -> Ten Brushes
2. Set your favourite eraser preset to one of the slots and press ok.
3. Then, to configure the hotkey itself. Go to settings -> configure Krita -> shortcuts
4. Search for 'activate brush preset', and then set the hotkey you'd like for that preset.

And then enjoy.

As mentioned in other threads, if you wish to switch back to the previous preset, use '/', and if you wish to have a key that if you press temporarily switches to a given preset, that is something that Krita is currently not at all capable of and will require a full rewrite of the shortcuts system.