I'm using LR on my laptop, dual 2.4Ghz processor, 2Gb ram. Still, LR is very very slow, and I'm working with 6mp photos. All the power saving options are off and I'm not using other applications at the same time. Just so you get an idea of how slow it is, imagine this example, the tint on a photo is 10, but I want it to be 19. So I select the 10 and quickly type 19. Afterwards I have to sit and look at the photo going to a tint of 1, stay that way for a bit, and then add the 9 and display the correct tint.