Jim, unlike Thorsten, I definitely prefer LR4 (the latest release candidate is 4.4; I'm using the latest completed version 4.3).
You might be interested in this LuLa post, which discusses some of the benefits.
LR4 also provides for better noise reduction, moire removal, soft proofing, significantly improved ability to make local adjustments using both the adjustment brush and the gradient tool (including color temp and tint), as well as more convenient approaches to various print options.
I kept LR3 for a while after downloading LR4, but I haven't looked back.
I use the M8.2, but of course the same benefits will apply to the MM (except the ability to edit b/w using color channels, which I greatly value).
Jeff
You might be interested in this LuLa post, which discusses some of the benefits.
LR4 also provides for better noise reduction, moire removal, soft proofing, significantly improved ability to make local adjustments using both the adjustment brush and the gradient tool (including color temp and tint), as well as more convenient approaches to various print options.
I kept LR3 for a while after downloading LR4, but I haven't looked back.
I use the M8.2, but of course the same benefits will apply to the MM (except the ability to edit b/w using color channels, which I greatly value).
Jeff