I started using this functionality as soon as I got my hands on the 2010 release (back in April) and I wanted to give "mad props" to the Inventor Product Management team. As an atypical user, this functionality, in addition to the sketch blocks functionality, has expanded the way I use Inventor. It's intuitive and as a "first release" is acting very predictable from an end user perspective.
I just had to re-do a 50 part static model that I originally did with Inventor 2008 (updating the assembly to new standards & components). This assembly had multiple configurations and I did it in less than half the time it took for me to model it originally. That's a positive step forward in my book.
You guys (Inventor Product Management Team) get plenty of flack here on the forums (I've given my fair share) and I just wanted to give credit where credit was due (bad & good).