AMD Phenom II X2 550 Black Edition - Phenom II X2 Callisto Dual-Core 3.1 GHz Socket AM3 80W None Integrated Graphics Processor - HDZ550WFGIBOX

Pros: Fast and cool. Running mine at 3.8ghz, 1.4v on a NVIDIA 8300 motherboard with a Thermalright Ultra-120 Extreme. Under full load, it hits a whopping 40c. Cool n' Quiet still works too, meaning it goes from 800mhz 1.0v, to 3.8ghz 1.4v with no issues.

Cons: No amount of extra voltage seems to help it get to 4.0ghz, but that's pretty normal for these cores. I'm still happy with 3.8ghz.

Overall Review: Because the setup is so flexible and I'm able to run my RAM faster, it actually beats out my Core 2 Duo E8400 at 3.6ghz in Cinebench rendering, among other things.

Pros: The CPU is amazingly fast when it works.

Cons: I have been getting random system reboots without any BSOD and the next BIOS post reports "A Hyper Transport Sync Flood Error Occured during last session". This happens while web surfing, listening to music, and playing games. I swapped the CPU out for a 955 I had in my main comp and never got the problem again. The Bios on my board also reported the CPU voltage as being 1.28v with a requested voltage of 1.35. I tried upping the voltage to 1.4 and the BIOS reported 1.302v. Dropping the CPU voltage to 1.28 gave me a 1.08v reported and an auto underclock of the CPU to x13 instead of x15.5. The 955 CPU doesn't have these voltage issues on my rig either.

Overall Review: I am running an ASUS Crosshair III motherboard, 2x2GB Crucial Ballistix DDR3-1333 1.8v ram, Saphire Radeon 4870 1gb, Antec 750w Earthwatts power supply, and hopefully the PhenomII 550 BE once my RMA comes back.
If the new CPU works as it should, I will up this to at least a 4, probably a 5 if it OC's well and/or unlocks the extra cores.