I updated from LR3 to LR4.0 yesterday and I observe a significant delay when I move sliders in the develop module. the delay exceeds often one second. It is not possible to use LR4 with this behavior. In LR3 no such delay happened.
I use WIN64 ultra a quad core @ 2.83GHz. 4MB RAM.
Do you think Adobe doesn't know there are some unhappy people out there? Do you think they're not aware that many of them are in their critical target audience? Don't you think they're working on it?
Don't you think if they had the "solution" they would tell us?
I think this is not a simple issue since it goes across platforms and doesn't seem to be related to how high end the hardware is. We're all hoping that someone in Adobe development will have an "AHA!" moment (or maybe already has) but they're going to make sure before they go out with it because they're gun-shy and don't want to have a recurrence of the same issues.
This has hurt them. How many people have put off buying LR4 because they heard about these problems? More importantly, how many people are holding off buying CS6 because they're afraid something similar is going to happen (me, for one).
By all means, keep the feedback coming to help them solve it, but 3/4 of the posts here are just plain whining.