I have been quite preoccupied on other parts of my life the last couple of months and haven't had a great deal of time to write about 40k. I have been planning a Dark Heresy Roleplay session and have just started running it, which is taking up a lot of my free time, in addition to other non wargame related things.
A lot of other blog sites have commented on how double force organisation charts are overpowered and they have quoted horrific builds like six squads of six longfangs with missile launchers to put their point across.
I personally don't think it is any worse than allies. If anything, its a lot more balanced than taking things from another army which is clearly not designed to be allied with your book. You also have to take another HQ and two troops, which is more of a points investment than the one HQ and one troops choice from your ally.
It can also help fix some of the issues certain armies face where some of their FOC charts are full of good stuff, while others have very little. This typifies some of the older 4th ed army books, such as Chaos, Eldar and Daemons to name but three.
Talking of which, the new chaos book hits shortly, I will be hopefully writing a review once I get it.