I'm not positive, but I think it's a memory bandwidth limitation for the mostpart. Between the video refresh (60hz 800x480x24bpp = ~69mb/sec) and the panning activity, I think the device is just saturated. Lowering the pixel clock should help alleviate some of that as well. I did try increasing the FPS in hildon-pannable-area.c (to 60), but it didn't seem to make much of a noticeable difference, so I'm pretty sure it's just a device limitation.