the pillow doesn't work for me -- makes it too high and too hot on my legs.
my fav way now is to fold a small lap blanket in a strip across my knees and put a piece of that rubbery shelf liner under my keyboard on top of it. that puts it at the right angle and it doesn't slide.
sometimes i just get close enough to my keyboard tray to buttress the keyboard against that and it works fine too.
I also have a thin piece of wood (like weatherboard siding) that i use on my lap sometimes, but after awhile it bothers my knees.
i'll tell ya tho, i have almost no prob's with my arms if i get that board in my lap. but i still revert back to the tray because i don't like having to move stuff to get up and down...