maybe it is slow as image viewer?
I can load 3000x3000 px images with Picasa really fast, also with the Windows image viewer. And takes really a lot of seconds with LazPaint. Why? Simple. Because they don't load the bitmap fully (try loading a big picture and quickly zooming in Picasa, you'll see what I say), they load a part of the bitmap, usually less than 1000x1000 px (or less), a
fast read, something similar that cell phones do:
http://developer.android.com/training/displaying-bitmaps/load-bitmap.htmlof course that's for image viewing, not editing.. (I think)
I recently downloaded Gimp 2, I need to compare both programs speed in similar situations.