OK, se I've been using my 2.3GHz 15" rMBP for a few hours and here are a few impressions
Battery life is fantastic. On my 2012 15" I was getting at most around 4 to 5 hours out of it. This one is quoting me around 9 hours which is great.
When using the Iris HD graphics (haven't tried the 750M yet) this machine is smooth. There's nothing anywhere near the lag I got on my 2012 machine.
Unfortunately the screen temperature is not uniform across the display. On the left hand side it looks yellowish and almost dirty, whereas on the right it's more neutral. Plenty of people have gone through this kind of thing before with Retina MacBooks so I won't labour the point, but it's bad enough that I'm going to return it. I haven't decided if I'll take a replacement or a refund yet, but I don't think there's any point in waiting out a "fix" for this at the factory, experience would suggest that it seems to just be the luck of the draw.
Here's a photo:
Image
+1
I don't know what to do. I need a new laptop but at the same time...that screen. I keep trying to say to myself i'll mostly be looking at my Cinema Display but that isn't a good justification. Why can't panel manufacturers just get this right.