Does the desktop version start to lag for you if you enable opengl? Gemini always uses opengl, so that could be the problem.

Krita desktop version  is running smooth with opengl enabled, texture buffering turned on and filtering set to high quality. There is no brush lag, and zoom rotate and pan all work smoothly.

Krita Gemini on Steam, as you mention, doesn't have an enable option for opengl. And doesn't seem to make any difference what the texture buffering or filtering option is set to.

I am using 64bit windows, BTW.
I have also set gemini to "Beta" in Steam's settings to keep up to date with any fixes.
At the moment, "stable" and "beta" perform the same for me.

I wish I could give you better details, but my technical knowledge is limited.
All I can do is report from my experience, and I am seeing a vast difference in performance between the two programs.

Yes, thank you very much for your information! We're trying to figure out why that is -- it doesn't happen everywhere.

Oh, in sketch mode, does it matter whether the color selector is visible?

This issue has been transient for me.
Normally, I use desktop view and for the last couple of sessions things were working much better.
Once I switched to sketch view and tried to use the color selector, all manner of buggy behavior ensued. The brush got stuck in color picker mode, the fonts on sketch view resized themselves to about 12pt, the cursor started lagging, then It crashed to desktop.

Upon re-launch, I experienced similar problems, I then toggled to desktop mode, and had the same sort of issues that I described in my initial report.

So apparently for me, if I go directly into desktop mode, I have no problems. Once I use sketch mode, some problem is triggered that persists for the rest of the session.

system specs:
Windows 7 x64 
12Gb ram
Nvidia geforce gtx 560m
Intel i7-2630 @2.0GHz
Wacom 13HD

Other details, I don't know if relevant, but may be. ( just in case sketchbook mode relies on them)
I have "Tablet PC Components" uninstalled (because it was interfering with the wacom driver)
I also have "Use windows Ink" disabled in wacom properties.

Could you paste the exact version string from the about box? We fixed an issue quite recently that would explain what you experience, especially if you use images with multiple layers.

When I launched Steam to check the version, Krita Gemini updated itself automatically. So I'm not sure If I'm using the same build as before.

 The current is Version 2.8.1 (git 0b3f51d) (x64)

 I launched it and found that it still isn't working properly for me.
I opened a multi-layered .kra image and it seems to work fine  in desktop mode. 
I then switched to sketch mode and happily, the cursor lag is gone. It draws and tracks smoothly, But I am getting an occasional pressure blip at the beginning of a stroke ( kind of like a splatter of ink from a fountain pen)

But the popup palette doesn't work at all in sketch mode, I was able to select colors through the menu at the top of the screen. When I switched back to desktop mode, I found that the brush no longer makes any marks. I have to relaunch the application to get it working again. I repeated this several times with the same result each time.

hope this helps.

I am experiencing a similar issue on Ubuntu Gnome 13.10 with integrated intel card.

However, I noticed that brushes that are set to 'wash' mode are a lot faster than brushes set to 'build-up' mode. Perhaps this is related?

For me, lagginess already happens in desktop mode for Gemini, Sketch-interface is even worse(With brush strokes coming out as poly-lines). Checking with Sketch as the stand alone program, the lag is really obvious there as well.

In sketch mode, we've got a problem with Qt forcing us to use double-buffering, which can cause bended lines especially if the image is largish. It's not something we can do a lot about :-(

I'm sorry, we had to drop support for the sketch and gemini variants of Krita because with the existing code, we couldn't make it work with Qt 5.

after deleting and then re downloading, krita still lags in brushes. cannot draw with them.

I was using an older version of Krita, and I was working on an image. I resized the canvas, and it started lagging. The type of lag is that I would draw a line, but it took about 2 seconds before the line actually appeared, making it very difficult for me to continue on the drawing. I updated to Krita 1.2.1 hoping it would fix the issue, however, it didn't make any effect.

Also, it isn't just my computer lagging, since I ran a scan program and a cleanup program and everything else on my computer is running just fine. 

Also, if it helps, the computer I use is a Toshiba, and is running on Windows 10. The art tablet I use is a Huion H420, and this is my first issue I've encountered in the month and a half I have been using these products together with Krita.