Looking at the history that Nik has, as well as the other products they acquired, it seems like photo editing in general was the target. Something to make Picasa a (hopefully) better product in the long run.
Picasa is like the Google+ of social networks, it had some loyal users who want it to be the next big thing. But that won't happen any time soon. Google will invest in this niché premium market for tablets. With the incoming Nexus Phablet and November's rumoured 10" tablet, they'll try and prove that Android offers more than casual/convenient usage.
I know Snapseed is popular, but I think Nik is actually more known for their other products, at least with photographers.
Silver Efex is easily one of the best black and white image processing tools around.
In Nik Software's case, it feels like the acquisition was a good balance between acquiring a team and acquiring patented technologies (http://www.google.com/search?tbo=p&tbm=pts&hl=en&...).
You can see the interface in action on their website. Load the following link (http://www.niksoftware.com/colorefexpro/usa/index.php?view=h...) and then click on "Working with control points". It's in an embedded flash player so I can't give a direct link.