In a word, this is brilliant. It is also one of the best placements of in-game advertising I have ever seen. The "Sims" series has been one of the most successful games ever, with the 100 millionth copy sold in April of this year. It's crossed the gender gap, addicting girls as well as guys. So with the infrastructure and demographics already in place, this was a fairly safe placement, and will likely bear Ikea nothing but good things.
I don't know the specifics of what took place behind closed doors for the Ikea and H&M packs, but I have little doubt that this was a paid placement. However, I also have little doubt that it was worth it, especially for Ikea, which offers fairly big-ticket items with a long purchasing cycle.
Less than a week after launching the Ikea stuff pack, EA launched a Sims Store, offering additional items for direct download a la carte. I won't be terribly surprised if I see other real-world items, perhaps in less quantity than a full-on stuff pack, appearing over the next year on the Sims Store.