Great for lower-end cards

Strengths:

-Allows for newer cards to work with older psu's
-2 LP4 connections to satisfy the power needs of newer cards
-Quality made, not loose or anything

Weaknesses:

-May not be enough power, any card that needs over 400w may not work with this adapter and cause a "not enough power" notice on PC startup
-Costly for a few pieces of wire and plastic
-8Pin devices require yet another adapter, almost doubling the total price
-If any more then 2 are used at once (i.e. for sli/crossfire) the system will fail to boot saying the psu is not providing enough power to the motherboard. (Experienced using two 8800 GT's in SLI)

Summary:

A great perk for someone wanting to add a graphics card to an old system without PCIe connectors, but may not be adequate for high end cards.

Also, a word of warning. I have heard of some people using Y adapters or cutting the cable to only use one LP4 connector. DO NOT use a Y adapter, cut the cable, or use it in any way with only one LP4 connector connected, this does not provide enough power and WILL damage your graphics card or psu.