This is a question I would love to know. I was actually just going to post something along the same line. I'm a graphic designer and would love to have the extra desktop space to do my work, but want to make sure the color quality is still good for photo editing etc. Right now I have 2 18" monitors running which is fine but cumbersome and not that easy to use with my pen tablet. I'd love to know which of these is best as I'm seriously looking at getting one.
I've seen comparisons of the apple vs dell;
http://reviews.cnet.com/4520-10442_7-6470175-1.html
but these were inconclusive to me and since HP now makes one, I want to see which is the best. If the HP didn't exist, I'd buy the Dell b/c for 500 dollars, you don't get that much more of a monitor out of it. I think you're basically paying for brand name although I've never seen the apple or dell in real life.
If the apple is actually outstanding and worth the extra 500, its probably worth it.
I don't do any rendering, but usually my desktop is littered with websites, spread sheets and such for research and the like. I'll have the cash to burn and I feel that it wouldn't be a bad investment. I already own a 24" samsung syncmaster 240T, which is excellent, but I'd like to have a monitor that can take more advantage of my graphics card. Plus the priceses have come down a lot.