Techgage just posted a review of the 4600+, AM2 version:

Besides clock speed differences, we can see the normal chips (5000, 4600) have a 89W power requirement, and the EE's, with the exception of the 3800+, use 65W. Due to the different thermal design, the 4600+ EE has a higher max temp of 72°C. This is a good thing, as I have had this chip run that high on the stock cooler. The most notable thing here is that the 4600+ requires 1.20vcore, while the standard 4600+ requires 1.30vcore. If anyone out there has a standard 4600+ and has run it on 1.20vcore reliably, please let me know. I am curious as to whether the EEs actually have a greater advantage in this regard.

From an overclocker/performance perspective, there are better CPU's to choose from. Energy Efficient aside, there are cheaper X2's that should perform just as well. One friend has an AM2 4000+ that is stable overclocked to 3.0GHz with 1.45v. Clearly, he wound up with a better chip than I did! Though 4000+'s are hard to find now, the 4200+'s are not. Comparing the non-EE 4600+ to the 4200+ on a popular e-tailer proved $79 more expensive. Now, this is not a big deal, really. However, for the $79 you save, you should still be able to get some great clocks out of this thing, and could likely even beat the max stable I have acquired with this chip here.

If you are really money conscious, then it may pay off to take a look at the 3800+ X2 also, which retails for around $150US. In the end, there is a lot of choice, which is a good thing. The entire line of X2's are well priced, but if you are to buy one now, I'd recommend either the 3800+ or 4200+. As for EE chips, I would recommend one only if you plan using at stock speeds. As we have found, the fact of EE didn't seem to help in our overclocking results of the 4600+.

In related news, Overclockers Club has posted an AMD AM2 3500+ Vs. AMD 939 3500+ comparison review:

Throughout this array of testing it seems as if the AM2 is merely one step behind its 939 counterpart. In the end, along with testing of newer games, I believe that the use of DDR2 memory is finally starting to pay off with the AM2 having a few clear wins. Whether or not this can be attributed to newer game engines or not, it will be interesting if we see future games pulling ahead on an AM2 platform as developers may be able to take use of that faster memory interface. Though the AM2 does win in a few areas, I still feel that if you are looking for a new machine, it would not be worthwhile to “upgrade” to an AM2 platform, especially from a socket 939 machine. Though it would be worthwhile to keep an eye on the evolving tech, because once the motherboards as well as the AM2 CPUs themselves mature, we may indeed see them taking the lead against the 939s.