First up, I was looking for information on the RIM-Apple war for the prosumer. A term that Wikipedia didn't carry much of. Thus far, Powerset looks like any other search:
Google on prosumer
Google nails it right away. But note that we're talking Wikipedia vs. the Web.
Powerset's interface at work
Next up, I was poking around for Bill Gates and Steve Jobs together. One item about semantic search may be user habits. I generally search on nouns out of habit. A semantic search could include Bill Gates stands next to Steve Jobs.
The need for Web indexing
The Google result shows how it's critical for Powerset to index the Web. That means Powerset will need a lot more funding or be acquired, an outcome that would make a fine exit strategy.
Where Powerset shines
Where Powerset comes in handy is big generic terms and items--the kind of information that's a Wikipedia specialty. My World War II search gives me a nice interface and key verbs that are relevant to my search on a high level.
And you can drill down on those terms. Here's a look at how PowerSet grabs verbs and assigns them meaning.
Powerset good for browsing
While Powerset is great for browsing I already know what I'm looking for--Italy's botched attack on Greece. Here's a look at the Powerset breakout on Greece in World War II. If this were a Web search I'd expect to find a lot more references. For instance, I'd expect some information on how Mussolini had to get bailed out by Hitler.
For comparison's sake I search on Google to find more information. Two Wikipedia entries lead the page. These items didn't surface on Powerset.