When I bought my 5D MK II in 2008, using LR 2 allowed me to shoot at ISO 3200, but results were noisy. Now, with LR 4, I shoot ISO 6400 images and with no NR at all, they are remarkably clean. Processing software has improved noticibly in the last three years, so I've gained about 2 stops when using raw, just by spending a few dollars on software upgrades.
@Mt Spokane, i have yet to install the beta version of LR 4 (was waiting for the full verison) so I am currently using LR3. Are you saying you noticed a significant improvement in RAW processing with LR4 to the point your ISO 6400 is like your ISO 3200 with LR2? And with no NR applied? Sorry I am just very intrigued and interested by your comments and not sure I understood...
If true then I will for sure get the LR4 beta! Thanks for letting me know if you have a chance.