Krita 2.5 locks up in brush scaling or canvas rotation mode with no way of confirming the adjustment.
Other shortcuts like "," or "." that do not require mouse input but do the same job work fine. It's just those that use Shift + mouse that are misbehaving.

Reproducible: Always

Steps to Reproduce:
1. Using version from ppa:kubuntu-ppa/backports.
2. Create or open a file
3. Use "shift + L click" or "shift + middle click" and drag on canvas to initiate the desired operation
Actual Results:  
If I use "shift + L click and drag": Krita gets locked up in the brush scaling mode. I can see the brush size indicator circle increasing or decreasing depending on the movement of my cursor but can't confirm the new size no matter what I do.

If I use "shift + middle click and drag": Krita 2.5 locks up in canvas rotation mode by continuing to rotate the canvas when I move the cursor. However, I am able to "free" my brush from this situation by slowly dragging the cursor outside the canvas and onto the menu at the top of the window.

Expected Results:  
When "Shift + Lclick and drag", then release: The new brush size should be automatically confirmed and the scaling indicator circle would disappear freeing the cursor from brush size scaling mode.

When "Shift + middle click", then release: the new canvas rotation angle should be confirmed an the canvas would stop spinning. 

Other than the packages from the ppa from which I got Krita, everything else is from Ubuntu 12.04 default repositories (standard config).