Some clarification on some of my more ambiguous requests
-Lock transparency in layers
Lock the alpha for a layer so that when you paint on it the transparency level stays the same while the color value changes. So if a pixel I'm painting on a layer with a locked transparency has a value of R:100, G:100, B:100, and an alpha value of 56%, and I go over it with a brush that has a color value of R:255, G:192, B:15, the alpha value stays the same but the color changes to the brush color.
-Separate palette for fill styles
Currently the fill styles are accessed via drop-down menu, but because you have to first click it, then scroll through it to find your desired fill style it takes at least 2 extra clicks to find the right one. If it were available on its own palette with as many swatches the window can show visible, it would be a 1 or 2 click job.
-Hold Shift while drawing to restrict line to horizontal or vertical axis
I'm not sure if MS Paint had this or not (don't think it did) but most every paint program other than that has the ability to restrict lines to the H or V axis while using the paint brushes. I didn't know this works with the Line/Curve tool, but it'd certainly be a plus if this were available for the brush and pencil as well.
-Ability to move canvas beyond canvas boundaries
This was an issue recently remedied in Photoshop (I believe in version CS2). Currently when an image has areas beyond the canvas boundaries visible, canvas movement is unavailable, and when the canvas goes beyond the limits of the screen size, the canvas can be moved up until the edge of the canvas meets the edge of the screen. Sometimes this makes it difficult to paint near that boundary. If the canvas could be moved when zoomed out instead of being constantly centered, and also be moved so that the canvas boundaries can be visible at the center of the screen when zoomed in, this would make painting much easier when using a stylus.
That last one is admittedly difficult to describe/understand... I'll see if I can come up with some pictures of what I mean for these.