Done properly, product placement can create a realistic scene and a general feeling of familiarity. Is there more to it than that? Do you think consumers notice the placement? Are consumers consciously motivated to purchase that product or are they actually reached on a more subconscious level?

The objective for product placement in TV shows and movies has more to it than creating a realistic scene and a general feeling of familiarity. The objective of contemporary product placement advertising is to create brand identification, recall, and affinity. The objective aims to influence and modify consumer purchasing behavior in order to generate increased sales through association of the product with favorite actors, situations, and TV shows.  
According to recent research studies examining consumer response to product placement advertising, consumers now routinely use the sophisticated level of their entertainment technology to tune out or skip traditional advertising inserted between entertainment segments. Some research indicates that because of this, traditional advertising will be replaced by contemporary advertising strategies, which include product placement. Minimal research has tapped consumer purchasing behavior following product placement in TV shows and movies; most consumer behavior research focuses on brand recall. While advocates of contemporary marketing strategies, including product placement advertising, represent the choice as generating more revenue from increased sales, this position has not yet been fully substantiated or confirmed through in-depth, targeted research.
JDR Group Marketing Agency, UK, "Traditional Vs Contemporary Marketing Strategies."
John Dudovskiy, "Product Placement as an Effective Marketing Strategy."
http://www.acrwebsite.org/volumes/8178/volumes/v25/NA-25