I described my initial impression on the difference between Lr2 and Lr3 regarding noise and detail in a thread over at the RFF here:
http://www.rangefinderforum.com/forums/showthread.php?t=92060
I was really impressed by how well Lightroom 3 handles with the new noise reduction mode and much more detailed sharpening.
ISO 1250 and 2500 files are now clearly much more usable.
I actually use ISO1250 with the M8.2 now with confidence, whereas my former mental border was ISO640!
I have no experience with Aperture though.
Care - the samples, I posted at RFF were completely unprocessed RAW files from the camera - you see only the difference between the two Lightroom iterations!
Completely processed, the files can be very clean.
I made A4 prints from ISO12800 EPSON R-D1 files lately, processed in Lr3, that really reminded me on how my pushed TriX @ ISO 1600 looks - that was scary (mind you, the EPSON still rules in being pushed over the Leicas regarding banding and noise).